American Muscle, Ninosport, Summit Racing, Steeda, alot of people are great to deal with. Ive had good experiences with ADP performance. I think they are fairly new but they had a good deal on the catback I was looking for.
A UPR x pipe is very affordable and is a quality peice. You can get one from UPR for around $160-$170 or so without cats. I matched my UPR with a Mac Flowpath catback and it sounds sick, but alot of people say that chambered mufflers (like Mac, Flowmaster, Spintech) dont sound good with an X pipe.
You really couldnt go wrong with Magnaflow Magnapacks or SLP Loudmouth-II's. Loudmouth I's are seriously loud and did I mention they are really loud?