If you're happy with the tone from your bass then a Sansamp would be overkill. If you're just after transferring the sound of your bass into a soundcard, but using a DI box to balance it, then you could use either a passive or active DI box.
It's always nice to have an active EQ on the box, as the sound of your bass on its own may not be the right sound in the mix, and being able to EQ it on the way in means less time fiddling later on. In that instance, the Sansamp (or similar) really comes into play.
The quietest (noisewise) one I've used is the Aguilar tone hammer - 2 9v batteries, mains adaptor or phantom powered. Alternatives include the already mentioned Sansamp. Also check out Dave Hall's stuff, he does an Active DI box that will run on all 3 power options already mentioned and are really low noise, i think currenty they're under a ton brand new.
if you want to spend even less money, then the Behringer BDI21 gets a lot of love around here. They're about £30 and it's basically a Sansamp clone. Not sure I'd gig with one, but you'll be fine with it in the studio.
HTH, Paul.