I would say that if you're going to upgrade from your stock cymbals, you only do it once. That is, save up and buy one good cymbal at a time until you eventually replace your whole set. Starting with the cymbal(s) you use most (hats for most) and/or the one(s) that sound worst of your current set.
Zildjian and Sabian have sound samples on their websites of the various models, which will give you some idea what you are looking for. A lot will depend on the style that you mostly play. I do a lot of acoustic stuff, so I'm drawn to the mellow-jazzy sound of some of the Zildjian K Customs.
Once you have some idea what you're looking for, go out and test some out (preferably with the same sticks you play at home). Check used places, too, as long as they're in good condition.
If you decide to ignore what I say (

), then go with one of the basic sheet cymbal packs (Sabian B8, Zildjian ZBT, etc.), which may sound slightly better than what you're using now. However, plan on upgrading again, because you'll soon tire of how harsh they are.