Bryston 4B St vs newer SST

I own the sst and auditioned the st against the sst. The sst is smoother and less fatigueing in my book. Because of that I hear more detail and enjoy the music more

I had a 4B-ST in use for mastering applications as well as critical listening and I can tell you without reservation that the SST amps are superior in EVERY category. If you want an amplifier to color the sound in any way, look elsewhere. If you want an amplifier to give you stellar resolution AND pack a wallop without flinching, get a Bryston SST. I am very pleased with my 4B-SST and have no desire to upgrade. The 4B-ST is a great amp. The 4B-SST just takes everything to a higher level.

They are actually very different than I imagined, judging from the posts... To me ST has a bigger lower mid, and seems to be more lively, while the SST is more refined in the highs, and the lows are so extended and tight, low miss aren't as forward but you can def. hear it, and its never muddy. your jaw will drop when you compare the sub output of both. The SST blows it away, and like the person above said, it doesn't flinch. On the ST The lows just sort of build up on the low mid and lows, but the sub range isn't as smooth and easy to hear like the SST. The ST has more bite as everything is very forward, but it isn't refined like the SST. At first, I thought to myself, you should keep the ST, but then I realized that the SST were just being more honest, and the fact that I can hear the sub so well. I decided that I had just reached a new milestone in audio, and I was about to make an immature decision if I kept the ST so I'm keeping the SST and not looking back. 

I was wondering what preamp you guys are using with the 4B-ST or SST. No doubt the amp will make a difference but the preamp is equally important.