Check out Summit Racing's website. They have a lot of low cost options. You can also buy mandrel bends from them if you want to just make your own exhaust. There is nothing about the HKS exhaust that is special that you couldn't do yourself.
I have the OBX over-axle exhaust (
http://www.ebay.com/itm/OBX-CAT-BACK-EX ... 0981920869 ) and it works well. Fitment is good and it comes with a bolt in plug that makes it relatively quiet for road use. The build quality is good and it sounds good as well. Over-axle makes it a lot easier to service the rearend too. I originally planned to build my own exhaust and after factoring in the mandrel bends and exhaust cans, it became hard to beat the cost of the OBX.