Congrats Strider on the ordering of the 7700. You will not need another amp at all.

Minh..go for the best amp you can afford. The 7700 is the best in 7 channel between it and the 7200. Common mode rejection is only available on the top tier amps(7500/7700/7900). The best hook ups are XLR, especially for longer runs but as XenonMan said you may or may not notice a difference. XLRs are not prone to static charges. Do you live where there are a lot of electrical storms?
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"There is one who comes after me who's sandals I am unworthy to unloose." John the Baptist