B&K amp differences

From my experience, I would not say that the EX4420 was light in the bass but it sure did not have the bass drive that the Acurus A250 then A200 that I replaced it with.

As far as the B&K's you mentioned, the EX442 will be similar in performance to the EX4420 just in an older package.  The others mentioned will not have the "high current" label with better bass drive but may be a bit on the "warmer" side.

Bill 

The last 2 B&K amps I purchased used here on A'gon went up in smoke.

That combined with the PrePro, I also purchased used here that never fully worked soured my interest in B&K.  

It's a shame, back in the day, they made a pretty good piece for the money. 

I had a 2140, it was a great amp.... I also had a pair of M200 Sonata mono amps that were also great.....  I regret selling them, but the monos were overkill in my system.   I went from those to a 50 watt tube amp and found that I didn't really need all that power....

The 2140 was  my back up amp for a few years,    great sounding amp for the money,  should have kept that one

I owned an ST-2140 a while ago and thought it was great for the money (used). If you look at the internals of their amps it's hard to see much difference within similar power ratings. If I were buying one I'd look for the most recent model, unless you want a bargain and are willing to recap it.