1) starting your pass at 70+ MPH is indeed a bit outside the performance curve. It's certainly not lacking but could use a little more in that range. It's speed limited at 106 sooo... 5star tune is decent and others as well...just make sure that it includes a tranny tune to go along with it.
2) There really are half solutions to the stereo. It's better than average for a stock system but if you're going to do it you should do it right:
FOCAL ES 165KX2
FOCAL EC 165K
DUAL JL AUDIO 10TW3-D4
Custom sub box mounted behind the rear seat
JL AUDIO TWK™ 88 SYSTEM TUNING PROCESSOR
JL AUDIO HD SERIES HD900/5
ZEN-A2B / DSP12A-A2B
The zen A2b is an absolute requirement as it acts as the interface between the B&O and any aftermarket amp/DSP. Without it you'll be forced to retain the stock amp and the upgrade will be a hack job at best. You can go up or slightly down from this configuration and swap out different parts but this is the upgrade that will deliver what you seek and yes...it's gonna be north of 1500-2k
3) You can't make the TTV6 sound good...period. Exhaust on these trucks is the biggest waste of money in the history of upgrades. You can make it louder but you can't make it sound good. Your new stereo will be the sthing you listen to anyway
4) If you aren't building the truck to suite yourself and other people's opinion is more important than you own then as those people from whom you want a compliment and see what they suggest. For me I tinted all the windows with dark ceramic, swapped the stock wheels from the 19 with the black beadlocks that were available for the 17/18 model year, installed bumber lights and backup lights...oh yeah...and I installed the "Raptor Assault" sticker I got from the school. I've had at least 20-30 compliments and several of those people wanted to have a full blown conversation about the truck....remember that not everyone is a truck person and not everyone who likes it will say something. You should be your own judge as to what looks good...afterall that's what makes it yours
One final thing...you should add the torque arm as it's the single best suspension mod you can make. All other suspension mods are personal preference but I think everyone would agree that if you could only make one suspension mod that makes a practical difference it would be the KHC torque arm.