Aster is on point. Sound modules are a HUGE space saver. If you are planning on building up a collection of synths over time, you want to go with sound modules. If you are going to use only one, you might as well cop an all in on e workstation, but you already have a sequencer (the 2000), so to me, thats just wasted money.
A lot of newer sound modules are actually more powerful than their keyboard counterparts. The Motif, Triton, and Fantom Rack variants all have way more internal sounds than the Keyboard versions. The only catch is, you lose the Keys and the sequencer. (and in the Motif's case you lose sampling)