Thanks for everyone's input, I've read all, including the links. I think I should restate my question, especially given my present layout. For me, it's not so much a question of whether to use long IC and short SC, or short IC and long SC. The question is will adding a pair of monoblocks connected by long balanced XLR cables really improve things? I already have short balanced interconnects (Blue Jeans Belden 1800F) between my prepro and multchannel amp, and long speaker cables ( Blue Jeans 10 AWG) to my speakers. With 7 speakers and 4 passive subs, there is probably 300' of speaker cable in my system, all running from the equipment rack. It is about 45' to the right front speaker, and about 38' to the left front speaker in cable length. Since I'd like to add a pair of monoblock amps, and since my 7' tall equipment rack is completely full, I'd position the new monblocks right next to the front left and right speakers. Doing it this way, I'd use a pair of balanced XLR cables, one 45' long, and the other 38' long. I have HT with bypass system, with both a Marantz AV7005 prepro, and a Pass Labs X1 stereo preamp. So, depending on use, either would drive the new monoblocks through a pair of long XLR cables. The Pass Labs X1 has a max output impedance of 750 ohms balanced, and 10 volts rms balanced out. The only spec I can find on the Marantz is a rated output of 2.4 volts in balanced mode. Then I could use a pair of short high end speaker cables, as Danny suggested to me. By the way, any recommendations on speaker cables that would connect to a five way binding post at the amp, and yet be able to be easy to strip and crimp a Electra Cable tube connector at the speaker end?