FYI: Backpressure is always a bad thing. Air velocity (or, high air velocity) is a good thing. The trick is getting the lowest backpressure with the highest velocity. Too big a pipe, and velocity is lost. Too small, backpressure is too high. True dual exhaust falls under the catagory of "too big."
So true, and so often people get it wrong.
The firebird muffler is probably the best way. HP-Racing makes an axle back that style for the CRX and HB. The y-pipe way probably won't fit under a CRX or Civic very well.
-Dustin