Not sure what kind of MMR you're looking to get.... The stock machine, with 1.5HP, should be good for 3-4 cu. in./min, if not limited by rigidity. And I know that both my knee mill, and my Novakon (which is MUCH bigger and heavier than the 770), is limited by rigidity, not power. I find it hard to believe the 770 will be able to make good use of more power than the stock motor provides. Using smarter (i.e. - constant engagement) toolpaths goes a long way towards mitigating marginal rigidity. But with small cutters, you may be more limited by RPM than by IPM.

Regards,
Ray L.