Another important question is what you have now. Some of it may be keeper stuff that is just not paired with the right gear. Other stuff may need to go, but can help foot the bill.
Assuming you're starting from scratch, I generally love the tone of Schroeder neo cabs. Unfortunately, a careful and critical listening will tell you they don't generate much in the way of dub-like thud. Great tone for everything else, and they do sound good for Reggae, they just aren't authentic. One of these cabs paired with some sort of big cab would get it done for you, but then you're pushing budget issues. It also has the advantage of doing a great job of making you audible through three guitars.
With your wide variety of styles, I really like a Line 6 preamp with a power amp. The Line 6 Bass Pod XT can be had for reasonable money and provides enough programming to get you quickly from genre to genre without fine tuning dials on stage. Nothing else that I know of will do this for you if you're looking for that versatility. With the X3 version out, XT units can be had at pretty reasonable prices, especially used. For a power amp, talk to Danno and see what he has left. A 1602 would be very good, especially if you can run 4 ohm cabinets, and a 2402 would be great. You should be able to get a Pod and power for about half your budget.
There are a ton of setups that will work for you. The one thing that doesn't work for any but the ludicrously rich is swapping setups every six months because you think there's something better out there. Build a core and add to it. The PLX power amp is a core piece that will never go out of style. If you decide to go with a one-piece bass head, don't ever sell the PLX because you may come back to it.
