i got some stuff on ebay before. i did buy a CD player on ebay but 2 in a row were defective (refurbished, same company, got my money refunded).
i picked up an older Alpine CD player on ebay, but it doesn't play CDRs or RWs, so it's just sitting in the box. was an $800 CD player when it came out, pure tuner, doesn't power speakers. when i can afford the right changer for it, it'll be going in my car. i paid i think $76 with shipping.
got a pair of ok 12" PPI subs shipped for $125. they sound pretty good, wired to 2 ohms in a sealed box and sharing 300 watts. they were brand new. they thump the Blazer pretty good.
got my amps on ebay as well, used. $110 for a pair of Kenwoods. one is a 25x4, the other a mono sub amp; 200x1 @ 4ohms, 300x1 @ 2ohms.
granted, with used stuff on ebay you're taking a gamble, but you can pick up some decent deals. even if you only save $30-40 after shipping on new stuff, that's still $30-40.