Rich; organic true balanced amp w good detail $6k

Cyto- thanks for the thorough comments/comparisons- didn't realize the VTL amps run their tubes that conservatively- a good thing. Question- you indicate the 'new' VTL450 signature has computer-controlled biasing. If one is buying these used, how 'recent' is this change? Also- are the 450 Sigs not 'room heaters'?

Tvad- thanks for Pass reco- was also thinking of their 30 watt XA-30.5. As for Israel, we talk often- he lives 10 minutes from me! There is no point though in even mentioning SS to him- he is a tube guy through and through-preferring SET's mainly...

Tvad: Great descriptions of those amps!
The Music Reference RM200 would have the clarity of the VAC but without the sparkle (very neutral, might not have enough flavoring for you), the RM9 with EL34's would be a little rolled on top and bottom, but the RM9 with 6550's would have better bass and more top extension but not as romantic in the mids (not as clear as the VAC's) (but not as tight as others or including the RM200 which is like SS on the bottom end).

I looked up on VTL's website and it looks like they have listed the newer version of the VTL450's which have some of the computer control circuitry in them for biasing. Maybe at CES this week it will be official or they will update the website. The S400 constantly bias during listening..As for heat... 16 6550c across two tube monoblocks generates a heat anyway you cut it, but in my small 16x12 room my lamms would heat the room 10 degrees in under 5 minutes.. Class A or Big Tube amps.. both are probably pretty close to the same heat output..

Your speakers are pretty effiecent and provide a high ohm difficult load that you should talk with the designer like TVAD suggested and find out what he recommends. The description TVAD makes for the Belles sounds like how some people descripe the Clayton equipment which I haven't heard.

Congrats on being able to make this kind of equipment choice... as this is the range of $$$ that products can be amazing across the whole frequency spectrum.

Some times Lamm ML1.1's show up which are 90watt tube amps (not hybrid) (not SET) and I'm sure they are amazing at approx ~10k and sometime 6-8k for the older ML1's. Don't buy Lamm's unless the owner has the original crates to protect them with otherwise you will have problems shipping them to Lamm should you need service.

Sutts, about the Pass, how much better do you think the XA-.5 series is? I ask because you will not find any used ones here since they are so new. I was thinking that many will now be dumping their XA's in search of XA-.5's. It would seem to me to be a good time to be looking for the XA's. You may be able to get a pair of XA-60's for the same price as a XA-30.5. Just a thought.

BTW, only the Belles MB-01 is biased into Class A, and it doesn't say if it's fully balanced or not. The Lamm's are very good, but I believe they are single-ended as well.
Here is a quote from the Belles website regarding Class A.

The key to accurate audio reproduction is the ability to resolve detail. To that end, David Belles has designed his first class A amplifier in 30 years. Everyone knows that class A biased amplifiers represent the pinnacle of what is possible in amplifier performance. However, designing and building a class A amplifier is no easy task. The first amplifier that Dave Belles designed more than 30 years ago was an class A amplifier known as the Belles A. Since that time, Dave Belles has learned what it takes to produce a truly great class A designed amplifier.

Class A design requires attention to tolerances, heat needs to be dissipated, power supplies need to be sufficient in order to produce an amplifier that does not compromise performance. The amplifier's power rating needed to be carefully selected in order to produce a unit that would drive most speakers at sound pressure levels that are satisfactory to most users.

Class A design is the best, regardless of what anyone would try to tell you.

I believe the VTL MB-450 Series II Signature with controlled bias is quite new. It was just reviewed in the Jan/08 Stereophile. I believe the reviewer (MF) had some issues with the biasing circuitry. Yes, I've been watching those too. Read the section entitled 'A Matter Of Reliability'.

FWIW, I have heard the Clayton amps. I used to own a pair of M-100 monoblocks. Very nice indeed. Possibly the best SS amps I've ever heard, and I've owned a few more expensive ones. The one nit I had about the M-100's was a low level transformer hum that I could not get rid of. I spoke with other Clayton owners who had similar problems.
I heard the new M-200's have new transformers, so hopefully Wilson has solved this dilemma.

Cheers,
John

How about the moscode 401HR;200 watts per channel, a 30 day in home trial period, it lets the owner do a lot of tube rolling that should not break the bank. The only requirement it does not meet is it not a balanced amp.

I have and really like VTL 450s from a few years back (no autobias and different caps than before). I think they are great. However, if you have high-efficiency Coincidents, the 450s might be a bit of overkill (like they are with my speakers). The Coincidents are reasonably benign loads as well so I think you could get away with less "beef."

Another couple of amps I can toss in the mix if you can find them used would be EAR 890(s) or EAR 861(s). They are both stereo amps which can be bridged and used as monoblocks. The 890 uses a KT90 tube and the 861 uses a EL519 tube (originally a TV set tube) in "enhanced triode mode". Both amps (and almost all EAR amps) have quite beefy transformers. They both have true balanced inputs, both work in Class A, both are quite easy on their respective tubes (the EL519 has a VERY long life) and both amps are very easy on the user (autobiasing, very little to do, long tube life).

If it were my choice, I might go for a PAIR of EAR 861s (which, when bridged, would put out 64W per channel). They have no feedback, are extremely linear, and I find the midrange and highs to be absolutely wonderful with this tube and depending on which Coincidents you have, you might be able to get by with a single amp just fine (the 890 would be no problem as one amp is 70Wx2). If you found them used, they would probably be in the price range for two (ditto for one 890). And in any case, you could get one, use it, and if you decided you needed a bit more oomph later, you could get a second. I love the tube...