I actually have a 10-string Stick (Purpleheart, Matched Reciprocal tuning) that hasn't seen much use since I started playing DB about two years ago.
It really depends on whether you plan to be running a stereo or mono signal. If you have the active Block or Pasv-4 pickups, I believe they both have stereo/mono switches that let you choose. People who go for a fairly unadorned tone, like Bob Culbertson's, can get away with running a mono signal into one amp.
If you go stereo, and want a combo with two separate amp channels, there aren't many options in your price range. Ampeg has announced a new 2-channel 2x8 combo--
http://www.ampeg.com/products.htm?pr...111&catid=13--
but no one here has tried it yet.
Stick Enterprises is working with the Italian SR company (which makes Schertler's esteemed PUB series amps/speakers) on a Stick combo but I don't think it's been released yet. I have heard Stickist Virna Splendore and bassist Michael Manring play through small SR combos--they both sounded great.
Aside from keyboard amps (which rarely have much channel EQ) the only bass amps with multiple channels tend to be pretty expensive (Acoustic Image, Epifani, Eden, Walter Woods). If you decide to get a single-channel amp you'll need some sort of external mixer (or auxiliary inputs) to bring together a stereo signal. Something like the DTAR Solstice would probably work well for both Stick and DB into just about any full-range combo.
The amp I use for Stick is an Eden WT-400. I run the bass side through various FX into the Eden's preamp. I run the treble side into a Boss GT-3 multi-FX unit which plugs into the aux input on the rear. The Eden powers EA or Bergantino 12" speakers and sounds great with Stick, BG, and DB.