Put your amp at the same end of the room as your speakers -- there's no reason for it to be w/ all the source & control components.
Balanced interconnects would be best for the long run from preamp to amp, but if you only have RCA connectors you might also do well with Belden-type cable (shielded, twisted pair).
I have a similar situation, but only about a 25 ft. run, and found that a cheaply-priced AR cable from Best Buy, advertised for subwoofer use (twisted pair, foil-shielded) makes an excellent long-distance interconnect between my Audio Research preamp & amp.