I'm assuming you're looking for a more full sounding crash that doesn't decay too much when you ride it. You'll need at leasdt an 18" cymbal and I wouldn't go any bigger then a 19" crash if you don't want it to be too overwhelming. However some people may suggest a 20", not me. If you already have a ride with a "Ping" sound, Trust me I wouldn't get rid of it. There's always a time when you realize you DO want a ping sound and you're sick of only having a ride that crashes and decays when you're trying to play some intricate sticking patterns). So I would suggest buying a second cymbal that can serve as the ride that you crash (or the crash that you ride).
Maybe you're other crashes are smaller (16") and that's why they're too overwhelming when riding them: they're producing more of a quick bite and you want more of a wash.
Try using Sabian AAX Crashes, in particular a studio crash (Not AAXtreme though). The AAX series is very controllable...you can just barely touch them and they'll respond fully (and more quietly) without hitting the cymbal really hard to get it's FULL sound out of it. But when you do bash the AAX cymbals hard, they'll give you the volume. Very versatile.
I don't suggest buying a cymbal with a "Brilliant" finish (shiny like a mirror when new) because they tend to sound a little glassier and brighter, thus giving the cymbal more volume (seemingly) as compared to a cymbal which is "Natural" finish.
Another option is Sabian "Sound Control" crashes. They're made with a flanged edge which helps control the overtones produced, and generally lower the volume of the cymbal when you want it to be controlled. They also manufacture Sound Control Rides.
Go to:
www.sabian.com, and listen to the cymbals you're interested in. You can read descriptions and listen to a recording of the cymbal either with a pattern, or being struck.
Have fun and good luck!