If you want to get away from rounds but not go all the way to flats I'd suggest a set of GHS Pressure Wounds. They're a great sounding and playing string. Very versatile tonally and they have a nice consistent tension across the set. I play them on my Jazz but they'd work just was well on a PBass and give you a little less thump and more mid punch than flats.
If you're sticking with rounds the D'Ads that come stock with the bass aren't horrible but they won't last long if you're playing much. When you change them look at one of the DR sets and find the one with the brightness level and feel you're most comfortable with.
Email Jason @ bassstringsonline.com and he can give some great suggestions depending on what you're looking for tonally and in feel. As a TB member You'll get a VIP discount on all of your string and accessory purchases. You won't get any better pricing, service and advice anywhere else I promise you that.
Congrats on the new bass. I'm jealous.