Would you rather drive a tricked out Toyota Camry or a Porsche 924?
Both bikes are good bikes. I find the Giant to be... Meh. It's a racier version of what you have with probably not much of an upgrade on components.
The cevelo is basically the same bike, just more exotic. Cevelo is a "cool" brand, but you're getting that sexy brand name, but not really a sexy bike and once again, not much of an upgrade on components.
If you are ready for road bike #2, then (imho) ditch the aero frame and find a bike with full Ultegra components in that 2700 to 3000 price range. You'll appeciate the upgrade in performance far more than you'll feel the (albeit more sexy) aero frame.