Luckily mine came with a billet aluminum rack and an Acerbis 3.3 gallon tank included. The rack looks top notch & cost $187. I really like it, but would probably have "cheaped out" and bought a low end one. I'm glad it was already on the bike.
The Acerbis isn't installed yet, it has a stripped mounting nut and the bolt won't come out, so it's time consuming to tighten it onto the radiator. I'm have issues with the TPS which I need to fix and will need to pull the tank a few times to work on it, so I'm waiting to permanently mount the tank.
If choosing a tank I'd go with whichever brand is largest because the WR is a thirsty bike. For my needs if I was choosing what to buy first it would probably be a larger tank. And your butt will demand a seat asap. I went with the Seat Concepts for the DRZ and was very happy, so I'll be calling them next week for the WR.
Hopefully you won't have trouble with the TPS. It causes the ignition to stutter at low throttle, high speed cruising, like when you're riding on the highway.
If you haven't yet, go find some big offroad hills to climb. The WR has so much power it just blasts right up them!
I can't believe Yamaha didn't offer these plated. I'm really surprised how few DRZ guys decide to try a WR450 before pouring so much into modifying their Suzukis, especially in states where it's easy to plate them. What do they spend trying to reach the performance of a WR? Isn't 50 hp the "ultimate goal" for a DRZ? I think an uncorked WR is about there.