It's not more versatile, it's not less versatile, they're different. A lot has to do with scale length, bridges, pickups, controls, etc.
A CU24 is an incredibly versatile guitar, and I don't think of it as only a modern rock guitar. It was designed with the ability to get lots of different tones, it succeeded for that reason, and is still PRS' best selling model.
But do you want versatile or different? Or both?
I think you'll notice more of a difference between what you have already and a 594. You'll notice more similarity between a CU24 and a DGT (I have both of these in my little handful of PRS').
A 594 is more like a Les Paul in tone. The bridge is quite different from what you have, resulting in a very woody, vintage style tone. And the pickups are different and more vintage-sounding. It's versatile, but who knows what your idea of versatility might be? There are no absolutes.
A DGT is essentially a version of the McCarty Trem (that dealers can still order in Wood Library runs, I had one before my DGT). The Grissom touches are the trem, the control layout and the pickups. That's all a matter of taste. The DGT and the McCarty are certainly versatile, but not ALL that different from what you've got in the CU24.
However, there are other PRS models worth considering, if you want both different and versatile and don't feel you need a Les Paul style tone: the Paul's Guitar and the Modern Eagle V. The 408 narrowfield pickups are definitely their own thing, and there's a crispness and beauty to their tone that's unique.