TeaLeaf: well the 735 is nearly half the price of the 930, but clearly much less hardware packed inside. a good buy at that price.
whatever i get its going to run 8.1 faster than the 620.
is there any overclocking apps for windows? haha. ram i think is the main issue.
2.2 GHZ quad core, 2GB ram and an adreno 330 does sound beast mode.
Don't be fooled by specs, sure the 2.2 GHZ is going to perform faster, but the 1.2 GHZ quad core with Windows phone 8.1 gives very good performance.
My 830 has 110 apps (yep I just counted them) and it is as smooth as butter still, whereas my old Galaxy S3 with a 1.4 GHZ processor and a few apps, runs like a dog with 3 legs.
1GB of RAM in the 830 and 735 is good too. And after all, it's a phone, in my opinion you don't need heaps of RAM or a powerful CPU when ultimately you are just taking the odd photo, playing a few games or watching the odd video.
If you are close to a Harvey Norman, or JB-Hifi or Vodafone etc, I'd recommend going and trying the 735, 830 and 640. I think you will be surprised at how well they perform.