get the alpine 7894... i have the 7893 cause i dont do MP3's because they dont sound good enough to me. the 7995 is a waste of money, the amp can be turned off in the 7894 and 7893... making them pretty much the same as the 7995 except the 7893 looses the mp3 capability. All of them sound amazing!
Pioneer really sucks... they only have a 94 db SN ratio... where as the Alpines are 103db. They are cheaply built and have a bad reliability rep.
Kenwood makes a nice deck... the only thing I dont like about them is the fact that the menu's are too complicated and there are too many buttons on the faceplate. Some models seem cheaply built.
Panasonic makes a very nice unit, I dont personally like that particuluar unit you picked out because of the face... but they do sound nice and are built well.
Clarion makes a good sounding, relatively simple looking unit... and as far as I know they are reliable and well built.
Sony, in my experience, they have a lot of reliability problems... every sony product i have ever owned has bit the dust in a year or so. They also have a lower SN ratio than the pioneers, at 90db.
I REALLY dont think buying these products off eBay is a good idea... buy them new from a dealer so you get the full warranty.