mono versus stereo ampflication

My feeling is that neither the 60W amp nor the 150W integrated are powerful enough, considering the 500W capability of your speakers, your very large room dimensions, and your interest in music that has wide dynamic range.

If I were you I would try to audition one of the higher powered X.5 (class A/B) amps, as your target selection, and compare its sound with the XA200.5 (pure class A), which I suspect is well out of your price range. Assess how much difference, if any, you can perceive between the sliding class A/B design and the pure class A. I suspect it may be small enough that you will feel comfortable choosing one of the X.5 amps, which provide more watts/dollar, as well as functioning less like space heaters.

To answer your specific question, no I don't think that a 200W pure class A amp is necessarily better sounding than a similarly designed 60W pure class A amp, other than, of course, on high volume peaks that approach or exceed the power rating of the smaller amp.

Regards,
-- Al

What speakers and pre amp do you have in mind???
I would select monoblocks from the choices given so far;keep speaker cables shorter;maybe even use balanced cables if the option exists as longer runs from the pre amp would now be possible if you can not locate the pre amp close to the amps.

I believe the Pass INT 150 is based on the Pass X150.5 (or X150)amp and the new Pass XP-10 preamp, not the XA.5 amp. As such it switches from class A to AB. There are some very positive reviews out there. I own the XA100.5 monoblocks and think they are great, so I'm biased. If you have the budget, I would choose monoblocks for the reasons stated above.

I think Audiofeil is a dealer and made a rather provacative statement above. Perhaps he can comment further.

A compromise is a "Dual Mono" Stereo amp on one chassy. In the most extreme case you would have 2 power cords showing the two amps share only the case. The advantage of this approach is that it gives better separation while saving on cost of another case , etc. My MF NuVista has three power leads from the power supply, one for each channel of the power amp and a shared one for the preamp. You cannot use this approach to put the amps next to the speakers but it has some real world advantages. But be warned, what constitutes "Dual Mono " differs not only by company but by individual model within the same company. For example , MF has called "Dual Mono " both amps which have separate power transformers for each channel and ones that have separate windings on the same transformer. A case could be made for either but they are not the same.

You can purchase TRL M225 monoblock amps brand new for only $5500. They put out close to 300 watts per amp and I have not heard better. The TRL stereo amp, no longer being made, beat the new $7500 CJ Hybrid (ET250S) amp by a good margin when I heard them both side by side this weekend in my friends home.

The new monoblock amps from TRL are a big step up from the old stereo amp so that should give you a good idea on how good they are.

I am confident you will find the m225 amps as good as it gets regardless of $$$$. They sound great with a nice tube pre like your AH.