My only thoughts on this would to be careful not to ruin the ride with the low profiles on the 19's, esp with the quality of our roads. The 18's might give a better ride but then as said, you'd need to get the height right to look good.
I'm a big fan of the look on 19's but having had 19" BBS LM's on my RS4 with 265/30/19 tyres the ride was very harsh and any bumps or holes were quite a thud that made me cringe every time
As for alternatives, i still dont want to change from my Monza 2's, i sometimes consider a change, then i clean them and see them shine in the sun and know they're here to stay - for now at least