Tube amps

It's the speakers which lack the warmth

I agree with the other posters above. I have WP7's and while they are voltage efficient at 92 db/watt, they are a difficult load in the bass. I tried some 15 wpc SET Cary Audio amps and the bass was flaccid and the dynamic range was compressed. Nice on voices and acoustic instruments but poor in bandwidth and dynamics. I then powered them on Conrad-Johnson Premier 140 and Audio Research VT100 Mark III tube amps, which are quite neutral tonally and sounded terrific on the WP's. Yes, they gave up some of the bass impact and dynamics of the best SS amp I have heard with them, an Essence Emerald II, but there is no beating tubes for warmth and dimensionality. I thought the C-J and ARC amps to be the best middle ground between typically dry and flat SS, and warm and dimensional tubes. Of the amps you list above, my gut feel says the Cary amp because of its multiple output tubes and probably lower output impedance, but I really think your best bet is one of the larger push-pull tube amps or a really good, powerful SS amp. The dynamics and bass of my Essence 250 wpc SS amp must be heard to be believed. The trick, as always with SS, is finding one that has some of the dimensionality and warmth of tubes. There are getting to be more of these recently, so maybe a good SS amp from C-J, Pass Labs, Jeff Rowland, or even a used Essence amp might be the trick.

Tube amps are usually not as good at handling low impedance speaker loads due to their high output impedances. A typical tube amp output impedance is about 0.5 to several ohms, while solid-state amps can have impedances down to 0.01 ohm, depending on many factors including global negative feedback. Because of this, SS amps usually have more control in the bass frequencies.

I have been using a Music Reference RM200 for over four years with my WP7s and have found it to be an outstanding combination. The RM200 has an extraordinary ability to deliver power to relatively low impedance loads, such as the WP7s. In addition, it has proven itself to be extremely robust and trouble free. They can be found on Audiogon for $1.7k to $2.2K.

I have paired WP 5.1 with SF Power 3 before. Despite the power rating, SF Power 3 was not able to drive the WP 5.1 without clipping. WP6 might be an easier load than 5.1, but I doubt it is very different. But if you want to go the tube route, I will suggest SF Power 2 over ARC VT-100 II if you want to stay within your budget.

Tarsando is correct about WP 6 is why the sound lacks warmth. If your goal is to have warmer sound, start with new speaker search.