Novice attempting to bi-amp. Help

even if you have 2 amps of the same model, I would still be weary of a vertical setup, unless they are a monoblock pair sold as such, or at least factory matched.

amps are like people, to a certain extent, it's a nature/nurture kinda thing.

IF you've got 1 amp that is used 12 hours a day, hard, and another amp that is used only for 30 minutes on weekends, it doesn't matter that they are sequential serial numbersa, they are going to be different sounding (to some extent).

With a Horizontal setup, the highs will sound the same from right to left, and the lows will sound the same from right to left.

With a vert setup, one speaker would be getting the benefit of a more broken in amp, while the other speaker would suffer comparatively from the newer amp.

Some manufaturers will match the amps, output wise for a fee.

Unless the amps were a pair of monos, or had been factory matched, I'd still use the horizontal setup, basically for right to left continuity and consistency.

How to perform a gain match two amp if they are the same made but different model has different power output? However both of them have output control L/R too.

With a decibel meter from Radio Shack. Send music or tones through each amp and get a reading. Set the level controls on the amp so they match the output for the tones on each amp. Make sure everything is the same - that is same tones and same distance from speaker for the meter with each amp. You can attempt to do this by ear but the meter is more accurate.