Adcom 545 vs. B&K st-140

Looking for a bargain amp to drive 4 ohm speakers and mate with tube pre....any thoughts?
Sound quality wise it is no contest. The B&K is many levels better than the Adcom. However, when it comes to driving 4 ohm speskers the early ST140-the one with the gold lettering and silver handles-is a little weak. Not very good current delivery. But the later ST140 with the red and blue lettering is a different story. It has no problems with 4 ohms and sounds just as good and in some ways better than the early one. I own both versions and have done an extensive comparison so I am not guessing on this. The Adcom while having a nice tight powerful bass is otherwise a very mediocre sounding amp. The B&K is just a much nicer amp with a sweet smooth musical sound that the Adcom can't touch.
If you want a little warmth go with the B&K. But if you want neutrality and your planning to add your own warmth go with the 545 MK2 Adcom. Sweet equates to colored but that can sound good too! Too much warmth seems to kill the clarity and detail in the music IMHO.
While I can't comment on the newer B&K ST 140, I'm in full agreement with Infinitebaffle on the rest of his post. I'd like to add that the B&K has a rather low-input impedance that might challange most tube pre-amps that usuaully have high out-put impedances. I can't remember the what impedance the Adcom presents.