Most likely onlookers will hear the same thing they hear in 90% of the SC videos you download: blower whine (not so much the exhaust).
Other than that, from many (many) prev exhaust posts, it won't sound very good. Get some resonators if you want to sound good. Dual 3" pipes is HUGE. You might be hurting yourself more than helping.
X pipe, check with Summit Racing or Jegs for plumbing parts.