For a discrete, effective and reasonably cheap solution, I would look at the JDM Integra Type R 4-into-1 exhaust header.

As far as a muffler is concerned, the USDM ITR cat-back works well.
So does the Apexi World Sport II.
If snow (and therefore rust) is an issue, the RSR ExMag series is made from stainless steel for additional corrosion resistance.

This is covered in the Integra FAQ as well, so I'd suggest you read through it as well.

Welcome to the board. :cheers: