I think the main thing to remember is that an Active bass has much more output than a Passive one, so you better make sure the head you buy can withstand it, otherwise you'll clip the amp and all that stuff. Other than that I cant really think of anything except to just make sure you get one that sounds good to your ears, and your audience's.
If your head or preamp has a separate gain and master volume (as most do), you won't have any problems. Also, many units have two input jacks, one for passive basses, and another low gain input for active basses. Indeed, some preamps have a -15dB attenuation switch as well.