Go with the CPU upgrade.

Although there is a speed gain between PP-2012 and PP-2014, 10 - 20% is quite optimistic and really depends on the scene.

I think I got a drop from ~11 seconds to ~9 seconds for a single nude figure by switching to PP-2014, but I rendered scenes that went from 30 min to 5 min on PP-2012 just by cleaning up completely wrong material settings. (And gaining much more realistic results, too)

So you can get much more by optimizing meshes and materials.

If speed, especially speed for animation is really your only criteria, then investing in a better machine is much wiser than upgrading to PP-2014. (And going from Poser 9 to Poser 10 will even give you less of an performance increase since they are both 32 Bit.)

Poser in general is very underpowered when it comes to animations.