Thanks everyone for advices. After looking on some reviews and amp specifications, I decided to go with Classe CAP 80, which was for sale here.
The Classe gear including the CAP line are described as having warm and rich sound with good soundstage- that’s exactly what I am looking for. Another thing that I consider important is that many posters here said Classe is a very good match for B&W speakers; in England, the B&W is the distributor for Classe and I don’t think B&W would distribute amps that don’t match their speakers well. The CAP 80 has a remote, something that CREEK 50I and Rega Brio lack. I know that it’s a CREEK 50IR amp with a remote, but I didn't find it on sale now, as well as CREEK 4330 SE and I don’t want to wait long. I do realize that an amplifier is a device designed for sound amplification, not for convenience of use, but the remote is a convenience which I would not like to sacrifice. The Audio Refinement Complete has good reviews but it's rated at 50WPC which is less than Classe’s 100wpc, and since B&W speakers have a relatively low sensitivity of 88 dB, I was afraid the Audio Refinement might not have enough power. It’s difficult to judge things like this without an audition, but it’s better to be on a safe side. Regarding the Vincent sv-129, it’s too few reviews on it and I was surprised that the price for the new one dropped to $400 while originally it was $900. This make me suspicious. Regarding tubes and separate amp/preamp- I think I am not there yet; for a variety of reasons.
I hope I will have an opportunity to compare CAP80 with some NAD (and perhaps other) gear next month in a local audio store. In this case, I will post test results here.