How much different is a levinson amp than a proceed

That's a really broad question since not all Levison amps have the same sonic signature, nor do all McCormick or Belles.

You don't mention your speakers which I would guess is where your problem might be?  

Also possibly consider a preamp with tone controls. When I find a recording a little weak in the bass, mids or highs I walk over to my preamp and adjust accordingly. 

I think its silly not to have tone controls. (unless you have a 'totally flat listening room", trust me you don't )

I worked in studios for years, you wouldn't believe the tone adjustments, compression and expansion used in every recording. 

You have a really fine amp and their is no history that I can find of it being weak in the bottom end.  

N. 

I assume OP has a Proceed HPA 3, a very nice amp.  I replaced my HPA 3 with a pair of Parasound JC 1 monoblocks, because I wanted to match a JC 2 preamp.  The JC 1s did substantially extend the useful LF range of my KEF Reference 107/2s down to 20 Hz.  If OP has the smaller Amp 3, that's a different matter.
db

The proceed avp  processor seems to be the culprit for the weak bottom end. I was ok with a classe amp,  but with the hpa3  it's weak