Mike
You are right!
I bought mine (2003 996TT) a few months ago having deliberated between a 996TT or 993TT for many months. The former being easier to live with as the performance is more accessible and so very smooth the latter being prettier although now maybe overpriced.
Your biggest decisions having set your budget (I would recommend £55K - £60K) may actually be whether you want silver and/or tiptronic! I found this very frustrating as wanted neither of these.
There were many features made standard in 2003 which is ok for the budget.
Personally I like the speed yellow BUT not sure if I could live with it!
Options/features that I thought were useful include sunroof, alloy interior kit, engine upgrades (DMS 500 already fitted), short-shift gearchange (the standard throw is ridiculous especially after the TT). I would have liked SatNav but the beautiful Cobalt Blue outshone that! BOSE is nice but not brilliant and I am enquiring as to how to upgrade this past the MOST obstacle. Standard exhaust sounds louder inside than out so I'm waiting for a Milltek...Xenons are standard.
As to whether to wait - IMHO, to pay 55% for a 3 year old car with 20K miles may not be the best bargain around a few months ago, BUT, I have enjoyed all of the miles since and it would be 3 years before the 997TT is at this value...?
Make sure you check all of the car's provenance and a good long test drive - be choosey. You must have an OPC inspection and a decent warranty - not with the outfit I was with [

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Apart from a clutch slave cylinder and the brakes (negotiated into the price and upgraded to Pagid blues at the same time as new discs with SRF) and getting used to the high speed 'patter' from the front end even after a good alignment seem to be the only marks so far - touch wood!
Sorry this is so long!
Krgds
Simon