I know its a different engine, but on my old 98 RS 3.8l, I had it soundling pretty close to a V8 at idle and up to 2-3k rpm.
I had an intake, headers, and a good conservative muffler. The muffler is the key!
Get the engine flowing with an intake and headers, then use a conservative muffler. Dont go for some high flow, super loud muffler.