If your an audiophile, then you might want to be careful with a class H amp on the highs! I tried it once and I thought it sucked. I used the PLX's Class H ones on the subs, lows, and mids, but on the highs it just didn't work for me. I switched to an Altec class A/B on them, and it made quite a difference. I don't know why, it just did for me (personal opinion)
On the other end of the spectrum, I've never compared it myself, but I always used a PLX 2402 bridged into each sub cabinet (4 ohm load). Many people told me that using a heavy iron amp in stereo mode would yield much better bass. This make sense to me because the amp would have more headroom to be able to deliver those punches. The 4 ohms per channel is leaving a bit if headroom on the big iron amp, and the 4 ohm load bridged (basically 2 ohm per channel stereo load to the amp) on the PLX is pushing it to the limits when your hitting close to clipping. The big iron being the RMX4050HD, 5050HD, Crown MA5002, and stuff like that.
I would imagine one would see the same thing in the midbass/midrange area, but those drivers normally aren't pushed too hard because that's where the hearing is most sensitive in the human's range of audio perception.
So, I would suggest tri-amping and having the ability to tweak a little if your a hi-fi nut!