Congrats on the car!
The factory 19" look pretty good but how much rubber can you fit on them?..and they are really expensive for a mild upgrade. Not really worth it I don't think.
The 18s are not too bad, it's just the skinny rubber that is a let down. I'll drive mine for a few months before upgrading I think as it'll give me more time to get the wheels I want. 19" Volk VRG2's are my choice at the mo...but that changes daily.
Enjoy your car mate!