Personally, I wouldn't touch the mufflers. Part of the appeal of the LS and all luxery sedans in general is a more sophisticated look, feel, and sound IMHO. It separates us from those kids driving around in Hondas with coffee cans sticking out from underneath their bumpers. I personally love the stock exhaust because it's quiet and anyone that has driven a truck or car with cat back systems installed ont he highway for any length of time will tell you that it gets old (the drone from the Flowmasters on my Expedition is almost unbearable during the 6 hour drive to and from school). As for tips, I say go for it. I wouldn't get much larger than a 3" opening otherwise it'll look like truck tips sticking out probably give you a flappy sound. If you want a real clean look, cut out some larger openings but make sure you do it right and get the bumper repainted and sanded so it doens't look like a hack job. If you DO decide to go for a muffler replacement, look at a multiple chamber set up if you can (especially with a v8) because that will give you a throaty tone without all the flappy noise. My LSE comes stock with a two-into-four set up that looks really nice, however the rear bumper is cut to fit this particular set up. Shop around and see what you can find out. If you do a search on YouTube, you can find a view videos of some LS's with Magnaflow AND Flowmaster exhausts. Take a look at these. Personally, I'd stay with stock but it is YOUR ride so make it to suit YOUR tastes.
