it would be the MTX 6001. its 600RMS.

you're gonna want to check what the impedance of the subs are. i think they only come as dual 2 or 4ohm. for that amp you're gonna want to have the 2ohm. if they're 4ohm, then maybe running only 1 of the subs would be an option for you as well.

i also would see if you can talk him down from 650, sounds a little steep to me.

only other thing is i'd say that amp is pretty weak to be handling 2 type Rs. they'll handle 500W each, so an amp around 1000-1100W would be a lot better and you're much less likely to fry your subs.