Whatever you do, make sure you get at least a dump back.
Cat back won't help you much, but will have a nice note (usually).
You can get the Liverpool Exhaust dump+cat combo in NRVOUS's thread delivered to your door for about $850.
Then you can either get a custom cat-back or a JDM cat back.
The JDM unit will usually set you back a bit more but it will bolt straight up, have a very nice flow rate and sound great!
If you can stretch for it, go with the Fujitsubo Legalis R, great flow, FANTASTIC sound and is pretty quiet when cruising.