Need Advice

Ok I was wondering what you guys recomend for what I would like to do.I am starting to play with the idea of an indash monitor/dvd player the main thing I want it for is:1.) the rearview camera (so the wife doesn't back my truck up into a 4' high Yellow pole in the parking lot again)2.) all in-one unit.. no hide 'em brains, Radio CD/MP3/WMA/DVD/Dual Disc3.) rear axle Camera input for off-roading4.) iPod expandability/control feature5.) Expanadablity for future upgrades,a.) GPSb.) the whole iPod Control unitI am looking into the Pioneer AVH-P5700DVD, but don't want to pay the sticker price. I am a Pioneer head unit fan, and think this will suite me.I most likely buy this unit off of e-bay (seems to be the best deal I can find going around $650). But want to do some more research before I fork out the ca$h.  Know any good places to buy it?Just to clarify, I dont really want to watch DVD's, but like the fact that I could download a crap load of MP'3 on a DVD and be good to go for a long time! I want the screen for the inputs, and want a head unit that will replace my OEM.The camera's seem to be pretty cheap, and I am looking for advice on the head unit. Does any one run a similar set-up or have a recomendation for a cheaper all in one unit?  I dont want to hide-a-box.  I have a 2001 toyota Tacoma Double cab, and dont have too much room for electronic hiding spots!