I don't know why you would want to get the MPK which is basically like a MPD and a MIDI keyboard had a love child.
If you already have an 1000 then I would just get a MIDI keyboard. Unless you want to software based then I could see getting the MPK, but having an MPC and MPK seems like unnecessary redundancy.
In the end it is all personal preference, and the ultimate decision should be based on what you are trying to accomplish. If you plan to stay in the hardware realm then just get a basic MIDI keyboard, if you plan on going to software then get the MPK and sell the 1000.
I think you need to take your time and figure out what exactly what you trying to accomplish and and go from there. I know we all suffer from gear lust, but you have to step back and think about what you're trying to accomplish. End the end they do two different but similar things, the MPC is a sampler and the MPK is a controller.
For example, MV's compared to MPC's they do the same things just one has more features than the other and one might be easier to work with, but they do both the same things. The MPK is just a MIDI controller, it doesn't sample or anything it just controls. So if you want a MIDI keyboard to you with your MPC then I would just get something like an M-Audio or something.
The main thing is that the gear doesn't make you a better producer or beat-maker the gear are just the tools used. What I would do in your situation is to sit back and asses and figure out what you ultimately want to do and what the end goal is going to be. It will save you a lot of money by figuring out where you want to go and how to get there, some pieces of gear just help with work-flow, then others will hinder your work-flow.
So my suggestion is to just sit back for a little bit figure out what you want to do. I've found that being limited in gear forces you think more creatively and actually makes you better because it forces you to find solutions around the short-coming of the gear you own.
That is my opinion on the matter at least.