Viridian is correct about the ST-140 having trouble with lower impedances, I have experienced this in extreme cases. I wouldn't pair it with a 4ohm speaker on a bet. The bass is not as big as "muscle amp" bass, but I find it voluminous with correct speaker matching. I can't speak to the Infinitys you own. "solid state like tubes" - this guy is right on. Probably explains why I moved up to a CJ Sonograph 400 in my main rig.
There's also a Mccormack DNA .5, just listed for $550 (steal)... out of the pricerange, but damn!
There's also a Mccormack DNA .5, just listed for $550 (steal)... out of the pricerange, but damn!