The best exhaust would depend on what you plan on doing. IMO, the best exhaust would be a complete replacement with a 2.5" header collector, high flow cat, 2.5" B pipe, and either a Spoon 2.5" muffler or a Mugen 2.5" muffler, since the Spoon is a regular canister design which limits the most noise yet still has good flow, and the Mugen is a twin pass muffler, which also lessens the noise. There might be a DC Sports TCS for the Integra now. That would be a way cheaper alternative for low noise.