19s would be OK for a 34, in most cases look good too. BUT, be prepared to sacrifice a bit of ride confort as they will be riding on very low profile tyres to keep the rolling diameter the same as stock. Also, if you are thinkin of goin 19s, should definately lower it a tad as well otherwise it would prob look like a 4wd. Again, lowering your ride would probably cause you to lose a bit of comfort but you gain on handling. 18s would probably be the optimum size most ppl go for nowadays + tyres are cheaper too. I've seen 34s with 20s as well if all you want is bling and do not care for ride quality.