Definitely go with a big honking roll of cord from Home Depot, either 12 or 14 gauge. (You don't want to go thinner than that.) Make sure it is UL rated for in-wall use. When I prewired a house I installed wall jacks that could accept banana plugs - one set just above floor level behind where the equipment rack would go in each room (I did the living room and one bedroom) and one set on the back wall above the main seating area. In the bedroom the jacks were placed to correspond with storage shelves built into the headboard of my bed. In the living room I installed a three-foot wide "floating" shelf above the couch and installed the jacks just above it near each end. Then I just attached banana plugs to wire running from the surround outputs on my receivers to the jacks behind the audio racks, and short lengths of speaker wire (the same stuff from Home Depot) and banana plugs to the surround speakers and plugged them right into the wall. Upgrades of the speakers or the receivers would have been a snap. (Unfortunately I didn't end up living there long enough to find out, but that's another story...
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It is true that a lot of cheaper "HTiB" systems use hardwired RCA jacks or proprietary connectors for their speakers (or have all the speakers connect through a "bass module) which is one reason they should be avoided like the plague. (Another is that they offer little or no room for expansion or upgrades, especially the ones that integrate the DVD player and the receiver.)
You
can find "Home theater in a box" from major manufacturers that are matched sets of separate components sold together at a slight discount. These sets tend to cost a little more than the more basic sets, but unless your budget is carved in stone, you will probably find that the extra flexibility and room for growth they offer is more than worth the extra money. (It is really annoying when you realize you can't get the most out of a game system you want to add to your system because there aren't any more digital audio inputs or HDMI connections available.)
Check the Denon, Onkyo and Yamaha sites, just to name three, for some competitve "HTiBs". You can also check locals stores like Best Buy and Circuit City which often bundle speaker systems with AV receivers and sometimes DVD players in packages that they sell at a discount. Sometimes an "HT in a box" doesn't all have to come in one box. (Also don't be afraid to haggle, even in Big Box stores. Many years ago I helped a friend buy a new TV, VCR and complete sound system at Best Buy and got them to knock a few bucks off the main speakers and throw in all the interconnects and speaker wires for free. Nothing ventured, nothing gained.)
Regards,
Joe