Looks like all of them cost a lot. I would check around for a local 'good' muffler shop and see what they come up with.
Cost really isn't a problem with me. I'm single, live alone, have no debt. Rent and utilities. So the cost I see for them isn't all that much of an eye-opener.
But yeah, was thinking about the local muffler shop axle back route. My understanding is the V-6 really doesn't need a dual exhaust, and a single actually makes more power. The advantage to the dual is strictly sound, but expect to lose a few ponies with them.