There are many brands are grades within each brand. We could have you spend $10k on some cables for your satellites, but that wouldn't be real cost effective.
To me generically saying 12 gauge cable for rear surrounds doesn't help answer his question. You could get 12 gauge cable off the roll at Home Depot or you could spend thousands on Tributaries. The Tribs would be a total waste on a HTIB and you wouldn't want to use lamp cord with a $100k system. What sort of satellites are you running and what distance are your runs & how are you running the cable? If you're using some B&W Nautilus speakers, Krells, or maybe some Revels for your surrounds I can see a good cable, but most people don't have that sort of budget. In this case we are dealing with a package - don't know if it is a Home Theater in a Box or not -which means the speakers will be decent, but they won't be audiophile by any means.
Try running 12 gauge or even 16 gauge cable under carpet - there's nothing worse than a huge hump in the middle of your room.. If you are running under carpet I'd get some flat cable...you'll still feel it some though. If you are making around your baseboard you can go with something thicker, but I wouldn't spend $100 on it for a Home Theater In a Box type system or a system that cost under $1200...you may spend $100 on your front cables in that sort of system. If you've got PSB, Infinity or Polk then it is gonna be overkill for your surrounds most likely...if you've got Bose then you can use Target cable.
I have spent the money for serious cables for my front, center, and interconnects, but I can't see spending gobs of money for your surrounds unless you have surrounds that warrant them. I have spend tons of money over the years upgrading from Monster to Audioquest (tried Type 4, Type 6 & CV-6 plus their coax & interconnects) and now Zu (Ash coaxials, Megulair component video, Julian speaker cables...still have a Monster Video 4 component video cable I'm using for HDTV but I'll change that out next year)...I've realized performance gains along the way, but when I rewired my satellites I bought a 100 foot spool of the 16 guage Monster THX and ran it around the base boards. I was using some Acoustic Research flat ribbon cable before that and it was adequate; unless you do a lot of surround sound music your satellites are not engaged that much any way.
I think the Monster THX cable you are considering would work well with your Onkyo system unless you are running the cable under carpet.
