As Ng mentions; Not an even match, and why not benefit from letting the tube amp carry the mids? That's where tube equipment provides the greatest sonic improvement. Unless you can balance the sensitivity and output levels of the two amps, you're going to end up with a seriously compromised response from your system. I actively bi-amped(tubes & SS) with one of these: ( http://cgi.ebay.com/DAHLQUIST-DQ-LP1-VARIABLE-LOW-PASS-FILTER-CROSSOVER_W0QQitemZ250612129926QQcmdZViewItemQQptZSpeakers_Subwoofers?hash=item3a59a5a086 ) (http://cgi.ebay.com/DAHLQUIST-DQ-LP1-VARIABLE-LOW-PASS-FILTER-CROSSOVER_W0QQitemZ280494334010QQcmdZViewItemQQptZSpeakers_Subwoofers?hash=item414ec3e03a), for 25 years(bought it in 1980), because nothing more transparent became available in all that time. I'm now using a TacT RCS 2.2X, for the room correction it provides(presently having an acoustically terrible listening room). If you aren't faced with major room/system interface problems; the Dahlquist DQLP-1 would be a simple way to successfully bi-amp, if you kept the x-over point at or below 400Hz. The DQLP-1 will also relieve both amps of having to amplify the full spectrum signal, and will enable you to bypass any x-over components between your woofers and midrange drivers, which(combined) will clean up your sound dramatically. If you do consider the Dahlquist; contact any seller, and be certain the piece is actually KNOWN to be fully fuctional, and having the original manual is nice too.