no no no no no no no no no.
Once more for good measure: NO.
Don't go spending £600 on the forge kit.
The AH fabs core is great, but it's £350+, AND you still need to make up pipes.
The forge cooler ISN'T as good for the A3, at all, it's a twin pass core, and retains the nasty pancake pipe and charge pipes, and it costs FAR too much money.
The £200 ebay kits arn't really man enough for hybrid power I wouldn't say.
I've just fitted the Wellycooler to mine, and the whole lot, including full 63mm pipes and the core and all clamps cost me £250.
Sure, it's a good bit of work fitting it, but no harder than fitting coilovers or a brake kit, and I've ended up with a setup that's far better than the forge in terms of cooling, flows amazingly, and doesn't cost the earth.
Check out page 27 of my build thread for more info:
http://www.audi-sport.net/vb/a3-s3-...track-car-nurburgring-toy-27.html#post1474854