I run 28B-SST2 with a VAC Phi Beta preamp. There is nothing forward about the sound unless it comes from the source. I believe that tag comes from folks who've heard earlier models, or lesser ones, or who haven't heard these specific amps in a system developed carefully around them. (Soundhut, forgive me if I'm wrong--no disrespect intended.)
The new 28s are special--full bodied, delicate, detailed, layered, even-handed at any volume from whisper to roar, and with ease under any load. I've never used a SS preamp with them, but I have used a Bent TAP-X AVC passive and the sound was not forward or bright. (Because they have an input sensitivity switch, they're versatile enough to accept some passives.)
They do need lots off current. The performance of mine jumped a level or two when I plugged each into its own 20-amp dedicated line.
The only real gripe I have is that they take an unpardonably long time to warm up--like 3 hours before they sound really good, and longer to be their best. Before that they're a little hard and flat, IMO. And I mean "warm up" literally: they become progressively warmer until, after four or five hours, they're almost as hot as pure Class A. At least mine are. It's tempting to leave them on all the time, 20-year warranty and all, but green guilt gets me.
I recall reading somewhere--maybe Audiocircle--that Bryston's James Tanner runs his 28s with Thiel 3.7. I know Bryston has shown the 28s with that speaker so they probably mate quite well. From what I gather, the 3.7 isn't forward, itself, like older Thiels I've heard.
I've never heard Karan amps and they might be even better. But I'd recommend trying the 28s, at least.
