75' RCA or 75' Speaker wire

My rear speakers in my HT will be on the far side of my ht room. the room is 45 feet deep so the speaker wire I ran is a good 65' long. Here is the skinny. My rears are floor standing rt12's. I have an Onkyo Amp now that is 2 x 135 watt that will be running them. Should I just use the 65' speaker wire or should I put in 2 RCA cables and then place the amp on that side of the room with short speaker cables to the speakers. Thx for the info! I notice on monoprice that I can only buy from them 50' cables though.