There is no XA600.5 only a X600. The A in the XA stands for Class A Watt amps. The X amps are Class A/B.
IMHO the Class A Pass Labs over the none Class A is the way to go if you decide on Pass. With the 802D you will need at least the XA100.5 but that might fall short. Then it would be the XA160.5. However the XA200.5 is the one to get but I doubt you will find that used in your budget. Maybe the XA160.5.
Please keep in mind that they are very heavy, large, can heat a small house and use gobs of electric. But they are great sounding in their Class A variant.
You asked about Class D in your OP. You should check out the Hypex Ncore NC400 DIY or the Hypex Ncore NC1200 OEM amps. Some OEMs provide in home demo.
For more info check the threads at http://www.audiocircle.com/index.php?board=197.0
http://www.diyaudio.com/forums/vendors-bazaar/190434-hypex-ncore.html
Good luck with your choice.