In general, I don't recommend buying Monster when starting out (priced higher than they're worth). If you've got them, though, I'd be hesitant to put money into replacing them.

For what it's worth, I'm using a mix of Outlaw and Blue Jeans Cables for my two systems, with some spare BetterCables speaker cables on my RR2150 (although I've also got a set of DIY speaker cables on the 2150 because I've got the old Studio60's hooked up until I can sell them) and some TMC speaker cables on the front speakers of my theater setup.