I got the B5 Flux.
Dont know how much you already know but here is some pointers.
Main weak spot is the stock tires, get some Hostile MX and you will get alot more out of it.
Next one is that the esc comes with deans connector, its not very good when you put batteries in series. Buy some 8mm bullets or simular. I use XT150 connectors. And then change the battery connectors to match.
Batterybox does not hold tall batteries (like the Zippy 8000mah) very well. They fit but you cant put the lid on and have to use straps around the chassie to fasten them.
Get a good powerfull charger that can charge atleast two 4S batteries at the time so you dont have to wait forever to drive.
Zippy 8000mah batteries is a good start. Cheap but great value.
A Low voltage alarm can be handy too.
Other than that you dont "need" to do any mods, it runs great.