The companies that you named off are Japanese car specialists, and do very little for the euro scene (the best you can probably hope for is their universal products, such as boost controllers, which obviously work on any turbo car).
As for the t-belt kit, it is very complete and is a good buy. Check
www.purems.com too - they and ECS carry a lot of the same stuff, but sometimes one will have a better price than the other on a particular part.
As for adjustable cam gears, I'm sure there are some, but I haven't yet come across them. Until you get into fairly radical mods though, including headwork and more aggressive cams (which aren't needed until your build gets pretty extreme, as there are guys making 500ish hp on stock cams), you won't really see much out of the adjustable cam gears. Maybe you'll pick up a horse here or there, but factoring in the cost of the gears, plus the tuning time on the dyno that you'll need in order to find any power that might be avaialble, you're proobably better off skipping them and looking into breathing and ECU mods for power. Ditto that for the underdrive pulleys - concensus wisdom here on AF has it that the UD pulleys do very little for useable output on these cars.
In your search for power parts, start here:
http://audiforums.com/m_55694/tm.htm
These companies all carry gear meant for the euro scene and you'll find tons of parts that you can use on your car.
timing belt service/kits/adj. cam gears
