800w RMS: 2x10" or 2x12"?
 

I currently have a MB Quart Ref 1.800 amp that puts out 800wRMS@1ohm.

It's pushing 1x15" Alpine Type-R in a vented enclosure.

The single 15" is great for the long, low drawn out bass, but I'm wondering if I'd be happier with 2x10 or 2x12" subs instead, i.e. better punch, harder hits, etc.

If so, should I go for 10s or 12s?

Anybody who's got any experience comparing with all else equal (same power, same car, etc.)?

Other details:
-Mazda Protege5 (hatchback/wagon)
-Infinity Kappas in doors
-Phoenix Gold amp powering Kappas 4x75wRMS@2ohm

if you are going to change anything, look into your enclosure. no reason you can't get snappy bass with that sub.

J has a good point. Give another box a try for what it will cost in wood. Stay to the smaller side, than the larger of the reccomended box size, with adequate bracing.
If not, I'd look into the two 12s. Except for all-out SPL, I think12s are the most versatile sub (but what the hell do i know)
My $.02

I had 2 rf 10s before at 500wrms and switched to 2 old w6s and liked it a lot better. Everything was the same except the box and subs. The 12s had a lot more kick to them than the 10s, and I didn't notice any sq loss

I would stick with the 15 and look at the enclosure.

Are you going to hear a difference as there is not much cone space difference. I'd also suggest a better box.