I'd check tire pressure (a big duh), treadwear, check if the treadwear is mostly even. I'd also check the air filter and transmission fluid.

How's your timing belt and water pump?

The quietest GOOD performance exhaust would have to be the Apexi World Sport (called WS for short) 2 or I'd check into the GReddy SP2. Both will run you about $400 for the entire piping and muffler.