well, it depends on what you are looking for in a sub.
the perfects are a pure SQ woofer with some limited SPL capabilites, the RF's are pure SPL woofers, with little or no SQ capabilities, and i think the alpines are a subtle blend between the 2, but still leaning pretty heavily trowards teh SQ side of things
also, it depends on which of each of these woofers you are looking at the SWR or type R, comes in both Dual 2 ohm VC and dual 2 ohm Vc designs... find out whihc is better for you application and go from there.
they will also ahve different power handling capabilites, look only at the RMS ratings, not the peak ratings, and for these subs, believe teh given numbers and even hazard taht they may be little underrated (;likely are)....
so for piound only, look at the Rf for SQ mostly look at the infinity, and for a combiniation, look at the type r's...
also find out how much you ahve to spend on an amp and go from there...