the clarion dxz615 ('01 model) has been going for $200 or less lately on ebay. There's one right now for $175 shipped. I've had my eye on those for months now, just never pulled the trigger. Sweet player, motorized aluminum faceplate, 5v pre outs, sub out. Can't ask for much more at that price.
I scored my 6400 for $220 shipped. It has all the features of the older pioneer decks, plus a few extra custom EQ curves (the last pioneer deck I had only had 1 custom EQ setting), and a feature called SFEQ that helps you create an EQ curve suited for the location/number of speakers in your car. It has a flip-down removeable face, it's XM ready, and the screensavers are cool as hell (chicks dig the dolphins!). There are probably better HU's out there for the price, but it's a pioneer and they have the best customer service of any company I've ever dealt with.
I spotted a Clarion DXZ725 for $199 shipped. I'd like to scoop it up but I found out that they won't take back my Sony. It's been longer than 15 days since I purchased it. I may as well keep it for a while 'cause I don't think I'll find anybody that will pay me close to what I got it for.