When I bought my 09 V8/M6 I told myself I wasn't going to change a thing. I drove it 3 times before ordering an exhaust. These cars sound like vacuum cleaners with the factory exhaust and you're absolutely going to swap it out. Having not heard a V8 or V10 with an aftermarket exhaust in person I didn't feel like dropping $5K++ on a "maybe I'll like it" so I went with the Rev9 stainless version to start. I figured I'd swap it out later for something more quality/pricey and at the most I'd have cost myself $1K for the Rev9 and 8 hours of my time to change it out, not the end of the world. Oddly enough, it fit great with some minor tweaking and it sounds pretty great for what it is so its still in there. If I could do it all over again I'd spend another $500 for the Ti version just for a bit higher pitch due to material resonance. If you're good spending some cash I know there's a forum vendor here who's looking for V8 cars to product test their exhaust. I'd love to hear a V8 car with the Inconel system on it. Their quoted price was very reasonable for what it is too...
My next change was to ditch the OEM HU/MMI. I tried to use a Bluetooth dongle but it was just too annoying to keep charged, plus I was still using my phone for navigation. Once the Pioneer DMH-WT7600NEX (9" floating screen) came out I immediately installed it with the help of all of the Enfig Car Stereo wiring kits. Mine was the very first one to be installed in an R8 from what I can tell and I absolutely LOVE it. It completely updates the the user interface with the car and with its design fits very well esthetically too. Pictures make it look like it stands out way more than it does in person, just and FYI.
After that I replaced the factory steering wheel with an Alcantara wrapped wheel. Its slightly thicker than the factory wheel but otherwise looks normal, no carbon or integrated shift lights as you'll see on some others. All of my vehicles always get the steering wheels swapped out for Alcantara ones. As the prime touch point, to me its just a much nicer feel. To each their own though.
After that I did just a few of the standard small engine related mods. Air filters and smooth tubes, just because they were on sale at the time. I also had a full carbon clean done which if there's no documentation of it being done before you should ABSOLUTELY have done as a relatively high priority. My car, with only 30K miles on it was very stopped up, we were all shocked at how bad it was and frankly how well it was performing regardless.
My car wasn't optioned with the carbon engine bay and by chance I happen to stumble into an amazing deal that seemed extremely sketchy and way too good to be true. Shockingly, it was legit, I didn't get stabbed and/or raped and I ended up with a full OEM set of engine bay carbon. I ONLY did this mod because of the insane deal I got just to be clear. I will say, that even if you pay normal used market price for this mod it does make a huge visual impact and is probably "worth it", but that's a person by person opinion.
So far the last thing I've done is the RWD conversion. To me, it makes the car way more lively and "sporty" feeling. At first I wasn't sure how I felt about it and actually re-converted it back to AWD after only a handful of drives. (I actually don't get to drive the car much unfortunately, only about 1000 miles a year on average over the my 4 year ownership now.) Last spring I decided to give it another try for a longer period of time and I'm glad I did. I actually enjoy it a lot and won't return it to AWD until I decide to sell it. Its a very easy mod that will only cost you $400 for the ABS stub hubs and a few hours on the lift. I should say that I have a lift and a fully stocked garage so its easier for me, but it should be a very cheap mechanics bill at a reputable shop.
Just food for thought...from one man's opinion.
Bottom line....drive the car for a while before you do anything. Listen to exhausts, join the FB groups and start looking for what you want in an exhaust. It's not a "if" mod, its a "when and which one" mod.
All the best,