Need long balanced IC's for tight bass

You should try SignalCable's Silver Resolution balanced interconnects. They are inexpensive compared to most others you'd consider; they're flexible, not too thick, and deliver very extended and articulate bass. (And the midrange and highs are quite competent, as well.) They might seem like underkill in a system like yours, but I bet they'd make you happy.

bluejeanscables.com is also a worthy choice, despite the low prices. One touted manufacturer of tube gear uses and recommends Belden wire for XLR connections. BJC uses the same stuff. I'm very happy with mine in an 11' length. Very flexible. I have a 25' pair of Canare too, great from top to bottom. I got those from a musician, I don't know how good he was but I like the cables very much. I just don't need 25 feet right now since the amp is closer to the spkrs. Good luck.