I've currently got a late '06 A3 2.0T quattro Sportback in S-Line trim with some tasty options. It's not the last word in handling, but it's very solid and quite rapid with a Bluefin map. All in all, I'm really happy with it - but it'll be 5 years old this year and I fancy a change.
I've also got a 15 month old daughter and (hopefully) plans for another sooner or later. We live in a city centre, so a bigger car is impractical and although I'm certainly no stranger to performance cars, I need something suitable for a small family. I'd love an S3, but it seems a bit crazy getting one with a new model on the way later this year.
This brings me to the Mk6 Golf GTi - it's a little more expensive that I'd like, but it looks like a great package. I'm considering "investing" in a 5-door with: Blue Graphite paint, leather, xenons, sunroof, RCD510, Dynaudio and the 17in wheels.
Just a few questions:
- Are there any factory wheel options other than the 17/18in Monzas? (they will get kerbed by my wife
and the finish on the 18s would surely cost loads to refurb?)
- Is the Dynaudio system any good? The BOSE in my A3 is pretty good to my ears...
- Does the GTi come with auto lights / wipers as standard? (can't see them as an option)
- How long 'til the Mk7 Golf?
Any experiences of running a GTi with a family would be of interest too! 
Thanks in advance.
Hey Ben
Welcome to the forum. Funnily enough, I was considering an A3 S-Line Black Edition as a potential alternative to the GTI and gave up on it for 2 reasons - build quality and the model refresh that you mention.
The demonstrator A3 I tried had done about 180 miles and the level of wear and tear gave me concerns about maintaining its condition long term. Its resale appeal would also suffer due to the later mark as well. Fortunately, the Audi and VW dealerships are opposite each other so I was able to do a direct comparison and it's a bit unfair on the Audi as the GTI is a newer design and benefits from better materials I think. The new A3 will be a fairer point of comparison.
I would take a look at the luxury and comfort packs, they've got some handy options in there. The auto drop mirror on reverse is useful for parallel parking in the city and auto folder mirrors are another good feature. The storage drawers I find invaluable, they're tucked under the front seats. You also get a luggage net to retain cargo (or a child in the boot if they misbehave) which can be quite handy from time to time.
I find 17" wheels to be fine driving in London, if I decided to change them, I'd upgrade them to 18" at most due to the potholes and poor road surfaces in general. Unless they've been seriously gouged, it's quite easy to fix minor damage. I caught an edge of a kerb and put a half inch scratch onto my front right wheel when pulling straight after a reverse park and it took me an hour to fix. There is a good tutorial online which is where I got the details for all the correct spray paint and lacquer colours.
I never bothered with leather, I like the standard GTI seats and mine look like they did the day I bought them. I've done about 5.5k miles. With kids, you'd probably want to have them AutoGlym sealed but if it comes down to personal taste then it's just that, personal.

If you want Quattro, you'd be looking at the Golf R which is Haldex not Quattro but the price quickly moves north of the Golf if you're specced from new. That said, I've seen a few high spec R's coming up on Pistonheads and similar for £5-£7k less than retail and some with sub 5k mileage. You do sacrifice boot depth due to the 4WD system if space is an issue for push chairs and all of that.
The GTI is a great car and I love mine, it's one of the best cars I've owned.
AGB