I personally would go with the two type r's. You will end up with better sounding bass as well as it being substantially louder. But that all depends on a variety of factors.
Unless your going to have 2 sx's then the 2 type r's over the 1 sx would be my choice but i would save my pennys and go for 2 sx's befor i blow it on alpine shizz
you probably wont be dissapointed with either. i love my single sx12. and the thing is, and what ill probably eventually do, you can always add a second sx and amp later on down the road if decide on the single one for now.