You'll probably get more for your money for a mk5, with a not much older car, I wanted a mk6 as I prefer them, mk5 gtis are looking to be affordable cars now. I paid 12000 for my 59 plate mk6 back in October but I could have got a late 2008 early 2009 mk5 much cheaper simply because it was an earlier model,not because it's an older car.
If you do luck at early mk6 gti make sure there is proof that the cam chain issue has been sorted either with a new tensioner or had a new engine in with the new tensioner or use the fact that there is no evidence of this as a bargaining tool for a better price then get the new tensioner fitted asap.