The first thing I ended up getting for my RX-7 was a cat back exhaust from Greddy. The only reason I got this was because it was cheap. I had a friend that had one used he was selling. Although nice in design and never failed me, this exhaust is very LOUD! I will probably look into getting another exhaust in the future and am testing several other exhausts in my friends car right now.
As for a Mid Pipe I got the SRM unit. It bolted right in and has all the necessary fittings. Not only is the car loud, but it smells because of all the unburnt gases from the turbo.