Probably a Flowmaster 40 series. I have one on my stock V6 S-10 and it sounds good....gets good compliments. Has confused a few people that were wondering if it had a "Mustang" 5.0 in it. Though a n/a V6 Regal with duals will probably sound more like a 90's 3.1 liter Z24.
Flowmasters are good for low performance V6 engines such as yours. However if/when you decide to get a turbo car, know now a Flowmaster won't exactly cut it anymore.