There are a lot of options of sticking with the twin turbo setup for the RX-7. People have put down like 380 whp with the stock turbos and with upgraded twins it's possible to hit 450 or so. It's definitely not the first thing to do, since the twins give you much faster spoolup than any sort of single turbo can possibly provide. Oh and then there's always the option of running a combo of a Garret GT35 and GT40, which always works nicely. No, these aren't monster numbers in the 600's on up like the Supra, but the RX-7 is a different sort of car despite the large drag racing community centered around it.

 

twin turbo is really worthless on a front wheel drive 4 cyl....

 

threads like this always make me wanna bust out this pic...