SLP's will run you in the neighborhood of $700, and have 1 5/8" primaries. Pacesetters will run you ~ $450 and have 1 3/4" primaries. Pacesetters have a somewhat sketchy history - there were some fitment issues (to put it lightly) on the first versions - I think they've since corrected this - and *most* everyone I know that has them - is pleased with them. Also - for ~$400 - you can get ceramic coated headers, which is pretty damn attractive.

HTH

-Swash