Pricegrabber.com is the best way to buy anything or ebay.Already pulled the link for the 6800 for ya
http://www.pricegrabber.com/p__Pioneer_DEH_P6800MP_In_Dash_CD_MP3_Player,__15727499. Difference between the Standard and Premier models is the warranty, but also there are
way more audio controls and preferences in the Premier units, thus better sound quality.
Pioneer decks are the best way to go! I had a 7700 when mine got jacked, then I upgraded to this
http://www.pricegrabber.com/p__Pioneer_DEH_P980BT_In_Dash_CD_MP3_Player,__26585757 plus the iPod adapter and XM I, never run out of music. Plus the Bluetooth feature rocks.
I also do some stereo installs in my spare time, so if you need any help shoot me a PM.