Anyone with W4S amps and preamp

I am using the W4S STP-SE Preamp with the W4S-ST-500 Power amp with Shunyata Altair XLR'S.These are powering vintage JBL 150A speakers (500$ for these in mint shape) and this combo sounds like way much more money.The source is a Sony 9100es -Modwright Mods- cd player for my den system.Also powers and supplies audio for Plasma tv.
The W4S amps have a warm,expansive sound and are capable of powerful bass,yet insightful detail.Speaker and room dependent,if you want power and volume these are great.
Best case scenario on the class "D" amps-buy a Spectron and a tube preamp.Long break in on these class D amps but they are worth the wait.Any help to you?

Thanks so much guys. This is exactly what I was hoping for. It has been a very long time since tubes have not been in the signal path of my stereo and I am twitchy. Unfortunately no way to audition similar setups within a 500 mile radius that I am aware of.

My preamp is a VAC Renaissance running balanced outs to the W4S ST500. Speakers for this setup are N802 and the system sounds great. I have never tried to run the amp single ended so I can't say what the difference might be. The manual for the W4S states that balanced is the preferred connection.

I am running the SX-500 monos into Maggie MMG's,

it is a great combination for sound quality, power, and price

My pre-amp is an Adcom GFP-750
definitely coveting the W4S STP pre...think it would be a nice upgrade from the Adcom GFP-750

I am running a ST-500 into a pair of Earl Geddes Abbey 12As, and it sounds great. I use a RHB Sound Dezign modified CJ PV-14L for a preamp, which means I have no choice but to use single ended cables. I am completely happy with the sound of this combo, it is very revealing.