In IPSC/USPSA circles, it is widely accepted that the lightest-feeling load for a certain power factor will be the one using heavy bullets and fast powder.
For example, almost everybody shooting 40SW to Major PF in USPSA is using 180gr bullets and a fast powder like Clays, N320, or Titegroup.
It is "easier" to meet a certain PF with heavier bullets vs. lighter bullets, since they don't have to go as fast.
The theory behind the faster powder is that the pulse gets over with sooner.
I'm not sure about the IDPA power factor rules for the class you'd be in. If they specify 125 PF, then your idea of a 135gr bullet is probably right on the money. Choose one of the faster powder with load data and go with it. I'm betting that Titegroup or N320 would give great results. It only has to be going under 1000fps to meet the PF, so you might need to up the load until your gun cycles reliably.
In IPSC, if you're shooting in Limited or Limited-10, you want to be at 165PF (plus a margin). Look at the 180gr bullets loaded to the maximum OAL which will feed in your mags and freely cycle in to and out of the chamber. Use a powder in the range of TG or N320 again. For Production, see my advice for IDPPA.
Hope this helps. I shoot 180's in my Limited gun for IPSC and 3Gun, but since it's an SV, I can load much longer than you can with your XD.