Just a warning, since you mentioned installing it in-wall. It MUST be CL3/FT4 rated for in-wall use under all National and Provincial building and electrical codes in Canada. If you use non-rated wire (lamp/zip cord, etc), it will probably work fine, but if you ever have a fire (even if not caused by the speaker wiring), the insurance company's investigators will look for any way they can to deny the claim, and if they find any evidence of non-rated wiring in the walls, they might (and probably will) stick it to you.
Do NOT use trailer cable (as suggested above) or anything else not specifically rated for what you intend to do with it!!!
Go to Home Depot, get the 14 or 16 ga 2-conductor in-wall rated speaker wire off the bulk rack (yellow or green jacket) and tape 3 lengths together and use that. It is very fairly priced and will meet all required codes. And no matter what anyone else tells you, it is equal in quality to any exotic name brand wiring for a fraction of the price.
You are unlikely to find properly rated multi-conductor wire that has sufficient gauge to carry speaker loads from a home theater amplifier. Using CAT5 network wiring will give you the rating for in wall use and the multi-conductors you need, but it doesn't have enough wire gauge to handle the current and will likely heat up and eventually short out.
Cheers
The REAL Joe