Yup, RMS is what you want, and peak ratings are just a marketing tool, usually used by the lower end of the spectrum companies.
Only piece of information we are lacking is the coil configuration of the subs. It looks like the only options for CVT's that I am seeing is Single 2ohm or Single 4ohm. If you could let us know what coils they have then a proper amp can be picked out.
If Single 2's then you will want 800W RMS at 1ohm
If Single 4's then you will want 800w RMS at 2ohm
Best bang for your buck new amps that will be decent would be Hifonics. It is true you get what you pay for with car audio gear, if you can find a nice used amp then you could make out well for the same budget.