Why are you buying a 2 channel Prime? Or are you running a memphis you're confusing first you say a Memphis1000 now you said you're paying $134 for a RFP600.2 please don't pay that much for a 2 channel to run subwoofers, get atleast an Audiopipe 1k or 1.5k for the same price. Also if you have the money SA-8s aren't bad but IMO a bit over-priced for what you're getting.
I didnt'r ead the part about those 10's being partially broken but if they're NOT blown then who cares about a few scuffs and a small tear that can be fixed with almost any glue/adhesive? For $100 I would buy those subwoofers in a heartbeat, then again it might be nastalgia of me owning 2 HE2 12's 4 years ago and slamming the block off 1k. I swear to god those things are severely under-rated and I don't even know how...
and you don't need a smaller box for 1k on 2 SA-8's if anything make the box a tiny bit bigger to get more output those SA-8's will take a solid 1k-1.2k daily I've seen 4 of them running off a Sundown SAZ2500. IF anything make a slightly bigger box for more output off that 1k.