A router is your best bang for your buck and you need the lightest tool you can get. The small makita, I cant remember the model, is your best bet. If you plan on building a more rigid machine in the future, go with the spindle.
I have to point out that I don't think your MPCNC will meet the cut capability that you are looking for. Those are very aggressive cuts for a flimsy machine like the MPCNC. It will cut plywood and is a good budget machine, but those feeds are too optimistic for the machines capability.