i have the standard 15inch wheels on my 147 and i want 17inch will this effect my car in any way?
First it all depends on which tyres dimensions you will use.
Recommended by Alfa, rims 7"x17" offset ET35 and 215x45/17 for the tyres.
Then you will not have any difference in terms of diameter, performance and fuel consumption.
I did it on my 156 as you can see below ...
Handling is far far better.
Tyres and rims are more exposed to kurbs, true !
For the snow ... well keep your 15" with a set of winter tyres if you wish.
Tyre wear will be identical.
Of course with a thinner tyre you will feel the road and the holes. Though i fully agree that tyres are not shocks ... a misunderstanding on many thread.
Noise is irrelevant unless you take tea in your car
I truly recommend you to do so ... as of course the look will improve and help the way you want to sell the car.
and if you look for rims ... alfa 147 cerchi e su eBay.it
go only for rims "originali Alfa".