If you're really trying to avoid ANY increase in NVH you may be pretty maxed out afa "go fast" mods go. If youre willing to take a little more feel of whats happening with the car, there are lots of small things like weighted shift knobs, short shifters, shift bushings, wider wheels & tires (ok those aren't a small thing) that you can go for.
You could consider LCA in the rear, they'll give you better launches when you feel like being spirited at a green or when you really get on it, and as long as you get street bushings you probably wont notice a difference in nvh (I didnt) - and those are a pretty easy install to boot.
Front brake GT conversions are quite good - the stock rotors on the v6 are a little small for the weight of the car, and they fade pretty quick. These of course cause no change in NVH, and look better too. They do require the use of a 18" wheel tho.
A throttle body will help produce some better throttle response and low end, making it more "street" fun. Again, easy install. Dont bother with spacers, they're almost certainly a gimmick (there's a reason they don't post dyno sheets with them)
I've replaced both sway-bars, and if you like corner carving, or having the back end wag, they're a great mod, and they wont affect nvh at all (just use plenty of grease so no squeaks). Id suggest replacing both if you do one, so you can make it match the way YOU drive.
A rear strut brace i've read will also tighten up the back end, and apparently will even help REDUCE some NVH from the back end (makes sense, more stability less motion) but I have no first hand knowledge.
A tune may affect warranty, but they take about 10 mins to return to stock, and realistically hundreds of ppl are running tunes from reputable shops (think BAMA & the like) without problems from the tune. Going all the way to the 93 octane is great, but even the 91 has brought me many smiles compared to stock. You can also probably see slightly improved mileage with a higher octane, assuming driving habits don't change, so to some degree it balances out.
You do seem to have done some appearance mods, but on that note remember that anything that adds a new ridge to the body (front lips, wings, flares, whatever, even emblems) will increase wind noise to one degree or another.
To reduce some extra NVH for ya, i'd recommend pulling the wheels and liners, and after a good thorough cleaning in there giving the back end a thorough coating of undercoating (obviously not the exhaust itself) Yes, it'll add a bit of weight, but I noticed an improvement when I did that and was happy for the trade off (you'll never notice the weight of a couple cans of that anywhere but a track, and even then were talking time attack levels to notice) or get it professionally undercoated. Usually not terribly expensive.
You may want to consider shorty headers. The installation is a wee bit more involved, but they dont really make the car "louder" with the stock cats in, just a bit more musical note from the back end. Again, nice bump in the usual driving rpm band.
Thats kind of all I can think of that wont produce a real change in NVH. Once you start moving towards a more performance mindset, then NVH is part of the deal, sadly. If you have questions, I'll do my best to answer them - I dont really know how mechanically inclined you are or what kind of results you dream of, or what kinda budget you want to have, so its hard to make recommendations.
In any event, keep modding your car the way you want, and don't let someone else's idea of what a car should be interfere, unless they're paying for it