500BHP does not need any internals upgrade. For clarity do you mean ATF ot ATW? I presume ATW!
1. Boost Controller
2. Turbo upgrade, don't think you can squeeze 500 out of even the uprated nur ones, don't need big ones. 2510's or if you want contingency say 2530's.
3. Bigger injectors, 600's will do.
4. APEXI ECU, not worth going V-PRO.
5. De-cat/change exhaust
6. APEXI Air Filters
7. Uprate clutch might be a good idea
Yes, Power FC. Comparable to F-Con, I just consider it a better option. You might also have to keep an eye on your AFM's in case they max out, you might need to upgrade to Z32 ones, which is a selectable option on the Power FC.
Everybody to there own. You need to compare price, functionality (what you need, not what you will not use), and so on. You could even just re-chip the ECU, but if you make further mods you cannot re-map easily.
V-PRO is far better than both, but it will cost more to buy, map and far exceeds your requirements.