Hi,
first, try to convert all AVCHD footage to Prores in Adobe Media Encoder...that is the best way.
It might help if your company does not want to invest into new computers, to check which new GPU works on your MACPRO, so you can possibly add some Nvidia 580/780 or some Quadro card...
Also, 10 Gb Ram is not enough on 8 core machine (I was struggling on new 6coe mac pro with 16 GB!!!!) , so try upgrading the ram at least to 32 Gb.....
On IMac, add more Ram, that is the only thing you can do...
CHeers!