You're not goign to see an increase with the R's unless Mark does something friggin insane with your box.
If you want to get louder buy two better subs (maybe two 10" mags or something that does good, maybe TDX 10's or D9 10's) and then upgrade your amps
That's my personal opinion, I know you dont wanna, but you're not going to notice a difference in output between anything you're going to throw in there, for the most part.
If you want to keep it like it is and upgrade output, save up for 10w6v2's man