Exhaust options...

Face it, most minis are 4 cylinders. Sounding like a souped up civic might not be the thing you're looking for. There are a couple good sounding exhausts that you can pick up. High RPMs will, most of the time, still bring the "I should install underbody neons" sound. I have nothing against the import scene, but I think trucks should stay trucks. So, put on a decent exhaust if you want a little more grunt. A couple of nice deep exhaust are the magnaflow, the flowmaster 40 series, the gibson and the borla exhausts. Another thing to consider when buying an exhaust is going to web forums and checking out what people are getting and what they like. Installing an exhaust on a mini is a little different from normal applications. You have a couple choices. First, you can cut the pipe way before the rear axle and install the muffler. This way you will never have to deal with the axle hitting the exhaust system, because it doesn't even come close to it. Secondly, you can go to an muffler shop and get a custom setup that can avoid any clearance issues that might happen when hitting the switches.

Here's a couple link to the exhaust companies I mentioned.
Gibson performance
Borla Exhaust
Magnaflow Exhaust
Flowmaster Mufflers

This forum might also help you because they have an exhaust message board
S-10 Forum
Even though it's a Chevrolet s-10 specific site, you can still find great information on any type of exhaust for your 4 banger.