Bear in mind a decat won't pass an MOT.

Custom isn't a bad way to go, the routing on an MR2 is pretty simple, brackets are simple.

If it's a good custom place they'll be able to make it to your spec with regards to noise.

As for off the shelf options on an NA, the best balance you're likely to find is a Blueflame or Mongoose.

Neither are

*loud*, but both sound much better than standard and are well made.

Both can also be used with a stock cat so you won't have an issue at MOT time.
