Bad situation here....
Jeeper seems like a straight forward guy......this "newb", IS 250, seems like an honest guy too. But YES, you did go about it all the wrong way. We know you're a newb and all but you should still know how to handle the situation a little better than that man. Let's give him (250) the benefit of the doubt saying that since he's a newb, he probably hasn't done much pming/talking to people and just happened to see the "Buyer Beware" feedback section and got hyped up and posted this bad feedback.........Um....sorry.....I don't know where I was going with that....lol!
But anyway, I think that both guys are legit in a way. Jeeper sold him a perfectly fine amp and I do believe that the amp isn't working right now. Reason being, I think it's an installation error. Is this the first amp in your system? Are you running the amp off a high/low converter? Are the outputs on your radio (aftermarket if you're using one) good? If you have multiple outputs, try a different pair. If it still doesn't work, try another HU if you have one around (or install the amp in a friends car with a known working amp/system). Are your rca's bad??? Are your speaker wires hooked up properly? Connected at all??? If you have aftermarket speakers, are any of them grounding out (that'll cause all the speakers not to play)???? Sure none of yours wires behind the HU (assuming you wired up the 4 channels behind the radio) are stripped back and are touching somewhere....bad taping job?!?! Are your speakers that you're hooking the amp up to any good?!?!?!?
Just a bunch of factors/things to look at man before you can just run on the forum and say that the amp, you bought from a legit member, is bad.
Try some of those things then get back with us on how you tested everything and how you know everything is good besides the amp. Good luck with the situation!
V.