50' speaker or 50' interconnect?

My equipment rack is at the back of my room and therefore I currently use 50' speaker cables. I have tried long XLR cables instead (moving the amps up by the speakers) but haven't had good results (perhaps due to capacitance issues with the cables).

I'm looking for suggestions for interconnects that can handle long runs.

I'd also be interested if anyone else uses a speaker cable run as long as me.

Thanks.