I used to use AIO+UPP+Souverän Paste Wax on our Ti Grey S60R, and I think it came out great. Then switched over to AIO+UPP+NXT+Victoria Concours/Red Wax, and I was pretty blown away with the look; especially, after couple coat of the VCW. Just recently, I replaced the AIO with Meguiar's ColorX, it looks just as good as using AIO...but sleeker than UPP.
You can easily get the most bang outta bucks with just UPP or NXT, with Ti Grey it's a bit difficult to get the depth under bright direct sunlight. But both UPP and NXT would give you awesome acrylic shine and slight depth yet still have the polymer based product's protection. But if you were to use some carnauba wax like VCW on the car, you'd still get the same acrylic shine (slightly less compares to NXT). However, with VCW, I noticed our car looked the best with some overcast....and I can easily take some few awesome photo shots of the car in the garage or underground parking garage.
I'll post some pictures tomorrow of what I did this weekend.
Oh, and I've always have good experience with Menzerna polishes to prep the car if the car gets a bit dull after few washes.