The As and FX series are certainly a step up. I think the A Custom splashes sound quite fine, as well as the FX Oriental splashes. However I think the Oriental chinas sound like absolute hot garbage, especially in the smaller sizes! The 19" K Custom Dark or Hybrid chinas are the only ones I'd recommend from Zildjian, personally I think Sabian and Meinl have vastly preferable selections. All depends on your ear though, so you should definitely see if you can try a couple out.Congrats on your A's!
Yes they are worth it! I suggest going to the store and trying them out.
as for the a custom splashes, try out the sizes first.
as for the chinas, the zildjian oriental chinas are what i would go for. They are great!