Lots of people have gone with a set of Hankook Ventus at @ $730 for a set.
( look at tirerack.com or discounttire.com, lots of other brands for around the same price )
18X7.5 means 18" wheel 7 1/2" wide
19X19 means 19" wheel 9" wide
225 and 255 are tire tread width in MM
40 and 35 are the 'aspect ratio' - means tire width to sidewall height ratio
( basically, the lower the number, the less sidewall between the rim and the road )