I don't see a reason to change the amps to anything else. If I did, it would be to get higher Watt amps. I don't feel I need higher watts though. My system peaks at 103 dB (maybe only 100 dB on the center channel because of the extra distance...). I don't listen to stuff at loud levels, so I don't think I need the extra headroom...
If I did upgrade it would probably be to the Bryston 28B SST on the front three channels. The rears and sides are (and will be) close enough to the listening position that I likely don't need more power there, but the front three are a bit further away in comparison. I wouldn't mind getting stable output up to 105 dB or more...