I did put Seymour Duncan Quarterpounds in mine (just because I had them already). Stock pickups are fine, but I wanted a bit more output. GZR's is also a good choice. No problem fitting them, it is standard P size on the bass.
If you do the switch, keep your old pickups, so if you change bass somewhere in the future, you can do the swap back and use your new pickups elsewhere.
I agree with others, a good setup is the first thing you want to do.
Don't under-estimate this bass because it's cheap. When I bought mine, I tried nearly every passive bass under 800$ that was available locally (it was my budget and I did'nt want an active one), and I finally bought it just because it was the most comfy I found (and that is an important factor when you play 3 hours gigs regulary).