EDIT: What do you have for hardware? Not sure what you consider pretty powerful but a system with a single 7870/7950/270/280 should get 100k PPD. You should be able to get a lot more than that if you have something like crossfire 290Xs or whatever.
Are you sure about those numbers?
I get 150000 with 2x r9 270(each do ~60k) + gtx770(~30k).
cpu=2500k, 13.12 amd drivers, 335.23 nVidia drivers.
Am i missing something? What can be done to boost performance beside overclocking?