I'm saying Ebay is very safe if you know what your doing and who to buy from. Occasionally you can find great deals, sometimes no. Right now there are no good deals for PSB's or similar quality book shelf's to piece together a surround system. Craigslist sometime is decent for used stuff as well, and you can usually demo the stuff before buying. You have to put the time and effort into it, good deals aren't going to fall on your lap, but they are out there. I bought a par of B&W nautilus 803's for 1,500.00 on craigslist about a half year ago. If you know anything about speakers you'll know that's a great deal on great speakers.
So I have seen the speakers i speak of for the price I'm saying. Might take some digging into and a little driving, but possible. Or buy a pre built generic 5.1 system.