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.
