'Why don't you just sell it an buy a VR6 or a 16v'..................... BORE OFF!!!!!
I would go VR6 all day long, especially since you said you aren't too bothered about economy
They sound ace, with a bit of fettling you can get m going pretty well and are possibly one of the strongest petrol engines VW ever built, no brainer for me.
Also, you can pick up a VR donor cheaper than a Valver donor at the min, seen 2 or 3 VR's go for less than £400 in the last few weeks.
If you had a bit more cash to play with then I agree with tweed on the V6 24v swap, quality engine, still sounds nice (although not as nice as the VR in my opinion) and 230bhp in a mk3 feels rapid

I personally don't think changing the engine affects the Anniversary spec of the car at all after all, its not like the Anni came with owt special under the hood did it, yes they never actually made a VR Anni but in my opinion they should have never made an 8v Anni, or put a GTI badge on the 2.0 8v at all 
The original GTi was 8v...not 16v....not VR6..........8V.
Agreed, but the mk3 8v was quite a poor GTI, no??? I aint slagging them off, my mk3 was originally an 8v and it never let me down but as far as GTI goes, hhmmmmm, not really.
Just like the mk4 2.0 GTI, really not worthy of the GTI badge IMO
Am I alone in my thinking here???