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Do you have the 4.0 OHV 6cyl, or the 5.0 V8?
On the intake side, I've run a conical open element K&N that attaches directly to the MAS for quite a while. This eliminates the stock air box, which is rather restrictive. The throaty growl at WOT is fun. You should get just a bit better mileage also. I know many use the KKM, I would suspect similar performance enhancement.
On the exhaust side, anything you install will be an improvement over the stock, restrictive muffler. I ran a Dynomax Super Turbo for quite a while, good performance and a little throatier over stock, but not anything obnoxious. About a year ago, I put on a Flowmaster 40, which sounds nice, is a little louder than the Dynomax, but again not obnoxious. As far as performance gains, sure, it helps a little, but don't expect HUGE gains.
Dynomax also makes the Ultra Flo, in the welded or stainless version. I'd go with the welded, same performance, a lot less expensive. This sound is comparable to the Flowmaster I have, just a bit of difference, but pleasing.
Borla and Bassani make a nice product, I've heard the Borla but not the Bassani. I think the Borla sounds a bit raspier than the Flowmaster or Dynomax. The problem with Borla or Bassani, in my opinion, is the price. They're great products, but are much more expensive than the others. Of course, because of their stainless construction, they'll probably last longer than the rest.
With the choices you've mentioned, I don't think you can go wrong with any of them. It's really hard to describe sound over the web, opinions are rather subjective.
Advice: Don't increase your exhaust pipe diameter from the cat on back, including the muffler. This will hurt low end torque some.
As far as Hp increase with the various mufflers, I think the differences between the brands mentioned is slight at best. A lot of people estimate gains from performance mufflers and open element air filters, but, in my opinion, without data from the dyno to substantiate it, they are just guesses. Sure, you'll gain some, but with the 4.0 OHV that is rated at 160 Hp stock, anything more than 5-10% (8-16Hp) is wishful thinking.
Again, anything compared to the stock muffler is an improvement. It just comes down to a matter of taste.