Using Adcom GFA-555s as monoblocks to power magnepan 3.3s in active biamp

I think the poInt is bridging disadvantages the amp’s ability to drive low Z loads. 
You have one. So why would you think it a good use of your gear?  The 555 was heralded as “high current” in its day (relative to its class peers, not Krell!), but bridging compromises that quality. I would try vertical bi-amping, however. 

Vertical biamping is an interesting idea - as I've always used different type amps it's always been horizontal.  But I have better amps than the Adcom as a stereo amp to use for the biamping (except the vertical as an experiment).  

Right now I do have a Krell amp as part of the biamp but it's on top.  I figure the better spot for the Nakamichi is on the bass. 

What sound levels are you hoping to achieve? At low to moderate levels you’ll be just fine, but if you’re going for loud, you may be looking for trouble.

All the best.

JD

Have you tried the Krell on the Bottom?

What sound levels are you hoping to achieve? 

Loud, but I can get there with my current setup and it sounds good. This was just a thought that maybe 800WPC monoblocks would be good to try on the bottom.  But not if they're going to struggle because they're bridged. 

Have you tried the Krell on the Bottom?

Yes, had it there for years and sounded good.  I thought the Classe CA-200 was actually a little better on the bottom with the Krell on top which is what I had for a long time.  I just moved the Classe so thought I'd see what else might sound good there. 

I think the basic point is there's a stability issue into 4 ohms with bridged amps, and if my goal is to be able to pour a lot of current into the bass panels, this isn't the most stable way to do it.

That's fine.  The Nakamichi actually is pretty muscular there.  I may try the vertical biamping idea at some point.  I wonder if the uneven load on the channels in that configuration would be a long term issue?