$8oo dollar budget

In a similar power rating (Ts Vs SS):Quicksilver Silver 70/90 or Primaluna 6/7.Might wait until the budget can be strecthed a little farther.

speakers are B&W 602.5 s3, Room size is 20x25.

10-07-09: Fromunda
speakers are B&W 602.5 s3

88dB, 8 ohm nominal (3 ohm minimum).

The 3 ohm spec rules out a tube amp, IMO.

Agree with Tvad, tubes will have trouble driving those speakers becuase of the impedance dip and swings and maintaining balance from highs to lows. That B&K is a pretty good amp for driving those speakers. I love tubes and only use them in my system, but not all speakers will mate well, yours are not likely to be a match made in heaven with most tubes amps, there are exceptions (Music Reference RM9SE) but they will be expensive. At your budget, I would stay away from tubes, unless you change your speakers first.

I would try to find a pair of b&k m200 sonata monoblocks as they sound tube like but I agree with Tvad and Pubul57
tubes at 800.00 budget would be hard to achieve.