I thought I'd chip in, since I was in the same boat as you, and my thread and name have been brought up ..
The S3 ticks a lot of boxes, it's nice to look at, I like the minimalist interior, it goes very well, it's grippy, reasonable on fuel, cheap to run and insure (well for me, being old helps
), the 4-pot turbo makes a reasonable noise, and the S-tronic burps are fun. Sounds great, I had an extended test drive and was sold, excellent.
However boredom set in quite quickly, I was seduced by Spangle Blue in the showroom (and it had just been added to the £550 options list, not a £2.5k option) failing to remember I don't usually like blue cars.
Long story short and I just found the car quite dull. I may as well have been in the 1.4 TFSi around town (the S3 is quiet even in dynamic mode), I didn't like the way it handled at speed, so the only thrill was revving it out for the S-tronic burp, and the opportunity to do that these days is pretty slim. I think that's the problem with most cars these days, they are actually too competent. The character has been ironed out. And although this seems a common answer to the 'my S3 is dull', remapping it and making it quicker IMHO does not turn it into a different car. The S3 does not lack for speed, making it quicker doesn't make it any more characterful.
I know the Boxster is a different type of car, but take one for a test drive, 5 minutes later and you'll understand when I say that the S3 steering is numb, too light and lacks feedback, most cars these days do. You feel connected in the Porsche, the handling is superb, there's no slack or roll. The engine is a delight, has character throughout the range, and the throttle response is in a different league. I have had a GT carnewal exhaust fitted and the flat 6 is aurally much nicer than any 4-pot turbo. I will not be buying a 781.
On to the practicalities, I've just been for a weekend away with the missus. 4 days. I used the frunk, she used the trunk, we had plenty space, it was comfortable, good fun on the B-roads up here, and I returned 34 mpg on the way up, which is only about 2 mpg less than I would get from the S3.
So, for me, speed is not the answer, neither is modding the S3. What you want to do (and I'm sure Jeremy Clarkson said this) is buy a car that's actually worse, but has character. For example if you need a 5 door hatch I'd try a Scooby, or a 135i for the engine/drivetrain. If you need 4 seats go look at a 5.0 Mustang, and if you only need 2 seats I can't see past a Boxster/Cayman .. 2nd hand now, as you WANT the flat 6, trust me