Unfortunately with s2k's its very hard to find a balance between sound and power... The hks sounds the best IMO, not too loud or too quiet, but it doesnt give you anything at all in terms of power. A 70mm single exhaust will give you the most power but is extremely loud and annoying to live with.

If your not going forced induction dont bother with exhaust. But DEFINATELY get a test pipe. I got the berk test pipe for $100, came with the CEL fix and I gained about 6whp. And now I plan to install the berk header for some more gains. But the test pipe is a must for any s2k in my opinion (unless you live in cali).

 

^Is ur tp 63 or 70?