I've been a 2008 WRX owner for about 5 mo. now and I'm looking to start modding my car a bit, only limitation being I don't want to void the warranty. What I'm thinking is cat-back exhaust, short throw shifter, new rear bumper cover (w/ diffuser) and possibly sway bars down the road. I've been able to find a good amount of information on these things and think I can more or less handle them, but I have just a few questions.

1- Is this the right part if I want to order a rear bumper with the diffuser? (one labeled "W/lip spoiler - Wagon - Wagon") autocenter.net (Also is there a better place to get it from, possibly?)

2- I've heard good things about the SPT Catback, is it still worth it with the introductory price gone? Is the "tuned by SPT" package still available and is it worth it?

Thanks in advance to any advice.