Gain matching of power amps

Kudos to you guys, you answered a question that I had in a different post. But, let me see if I've got this right.

I've got a Casablanca preamp, which is basically a big Theta card cage that you can slap different D/A output cards in and configure each output the way you want. I think (I don't have my manual here) that you can pre-set a gain for each output, so output set A could be configured with, say, 3 dB of additional gain over output set B, at 0 dB gain. If I then had an amp X with a gain of 26 dB and an amp Y with a gain of 29 dB, would I then achieve a uniform gain of 29 dB by hooking amp Y to output B and amp X to output A?

The reason I ask is because I always assumed that there was some nonlinearity in the gain as you increased the input voltage. I.e., that the gain you find in the specs is some average and is not a constant over the range of input voltages. Is this a dumb question?

Thanks for the info, I'm still thinking about what to do when I move in 1.5 mo. and can unpack some gear in boxes, and its food for thought. Martin Logan actually recommends bi-amping my Prodigys with tubes up top and SS below. I was going to use a pair of ARC VT100s I have, but now am thinking of watching for an old ARC D400 and using the extra VT100 elsewhere.

In my case, Ral, the Casablanca can be turned into an active x-over. All things being equal, however, I'm not inclined to go active b/c I'm not sure I can replicate the job the ML x-overs are doing and the marginal volume doesn't really mean that much to me.

I always thought the "purists" suggested avoiding an active x-over anyway to eliminate "yet another thing in the signal path"... (Obviously, doesn't apply in my case, 'cos the Casablanca is there anyway).