AidenUK:
IMO it's 18's all the way mate.. 19's on lowered suspension with a very low profile tire is asking for a rough ride quality. 
Spot on!
I've just changed my 19x9 rims for 18x8 rimz and the ride is like heaven in comparison....the rides better, handlings better, tyres are cheaper, cars faster, mpg isnt as bad etc etc...i could go on for a very very long while lol. Even getting them painted or coated is more expensive ( trust me ive done it )
18"z and some springs will look fine in my opinion.