No additional DI necessary (the R-out put is even marked DI) unless you need LoZ output (the "PODlike" version has balanced or unbalanced 1/4-inch I/O; the "Pro" (rack) version has LoZ, HiZ, AES and S/PDIF digital outs, and insert I/O). The "pod-like" version works great and is a real bargain for the money. Out of the POD, GNX, GT, Zoom, ToneWorks, etc., class of modelers, the Behri's are the only ones with a true, hard-wired bypass, which makes them particularly nice for (multi)effects-only use. Go to Behringer.com support for patches and a PC editor. The PODdie version starts looking like a little octupus by the time you get all the connections hooked up. All in all, the Bass V-Amp is a really useful bargain.
A lot of my friends use the (analog) Tech21 bass drivers for DI.
Some of them really like the ART Tube-MP preamps as DI units.
Good luck,
Paj
8^)