From my experience- I started with an outlet PB-1000. My chain up upgrades then went like this: added a HSU VTF-3 MK4 ($300 in great condition), then an outlet PC-2000 (at this point I moved the PB-1000 out and into another room; the PC goes 1hz deeper and has a MUCH smaller footprint), then a sealed 18" Optimax kit from PE driven by an XLS 2502. I have another PC-2000 arriving on Friday to get my fourth sub in my main room. The debate for me now is to go 4 PC's, move out the Optimax and put it where the PB is to go with another VTF-3, or move out the VTF-3, get another Optimax and put both of them in the back.
That being said, the 2000 is dramatically more powerful than the 1000. What this means for me is more meaningful low end extension at lower volume levels. If upgrading to the 2000's isn't going to hurt you in the wallet, I'd take the deal in front of you quicker than it takes a bass not to make it to me from my closest sub.