I suggest you save up the difference. I've seen it go for $450 (also try to see if seller is selling at best price).
A good camera like a Kx offers the features and performance that will last you for a long time. IMHO, pro-sumers like S90, LX3 or some cheaper option will just make do for a short span of time and their limitations (smaller sensor; lens options; less of DOF control; etc).