I ran 19's on my GTI which has basically the same suspension. It was a bit bumpy but ok when you bear in mind it's a hot(ish) hatch. When I returned to running it on 18's it definitely felt smoother.
I ran 19's on my mk6 too but didn't notice a difference in ride quality so maybe it's just my imagination.
The only thing to bear in mind if you have to pay for your own tyres is that the 19" tyres are a lot dearer, if not then it's not something you're going to give a second's thought towards!
The Santiagos are a pig to clean too if you clean your own wheels, there are tiny little spokes you need to get round. That's fine if you're a detailing obsessive or do a low mileage but in winter they're going to get a bit painful to clean. That said, they do look good.
I'd add park assist to the spec too, if you have 19" alloys especially - it works really well and at first you think it's a gimmick and just show it off to your friends. Then after a while you realise how good it is when you have a really tight spot to get into, its raining, you're running late and you don't want to hit an alloy wheel on the kerb. At times like that it's worth every penny. I miss it on my current car.
The Carbon Grey looks great though, a good choice of colour.