The fast guys (pro level) are all going really fast on whatever fins they are sponsored
C3 Venoms are fast, Tectonics Talons are fast, Deboichet has some very fast slalom models (not the Starboard Debs), Lessacher makes some really fast fins.
You cannot necessarily "BUY" speed.
You can buy all the pieces and still be slow, or you can tune what you have to get the most from it, and maybe be very nearly as fast as you would be on untuned and unbalanced top of the line gear.
The sailor makes fast gear fast (or faster) by lots of TOW and tuning.
You need to tune the rig, have the right spars, get the right fins, figure out where the fastest mast foot position is, then you can start tuning the sailor to make it all balance better so you can go faster.
You could spend a ton of money and still be slow. Good stuff, that works for the pros, is usually a bit easier to tune correctly, but do not suppose that you can buy a top of the line race sail, top of the line Tectonics Talon fin, put them on your Futuras and go out and beat iSonics with better sailors on them. It's not going to happen.
Unless you become a pro windsurfer and spend more than half your life on the water tuning and learning, you will always watch the guys who are at that level with a certain awe. They are indeed awesome and they make going fast and winning races look so easy.