At the moment I have 16inch OEM wheels as well.
I want to buy 18 or 19inch wheels for the summer and put on my OEM 16inch in the winter (for snow-vacation where chains are needed).
In other words; I would go for the expensive solution on short terms (this is cheaper on long terms). You don't drive on your expensive 18inch tires all winter;-)
Good luck with yuor decision!