I love the look of the magnaflow, and the sound seems to be good. Do I need to get a full catback, or can I just get the mufflers and magnaflow tips for that look?

 

I bought just the muffler (and added tailpipes & tips) because I didn't feel like ripping out a brand new I-pipe. If I had been dealing with an aging exhaust system, I would have done the whole cat-back.

Anyway, you can definitely do just the muffler and then maybe check their web site for the tips:
Magnaflow Tips

 

cool, but what are the downsides in doing that? Do I loose horsepower compared with getting the whole catback? Is it less strucuraly sound?

 

Personally I think gains between the full cat-back and just adding a muffler are neglible. Maybe 1-2 horses different. Now if your car is beefed up a lot. I would say the full cat-back would be better to get.

 

Is is less structurally sound? I guess that depends on who does the work. Just buy the muffler and tips and have your local shop do all the work.