I did this exercise last year. I had the VSX-60, SC-61 and then a yr old SC-55. (the 65 was more than i wanted to spend)
If you are into the ipad/iphone app (which is a major advantage PIO has had over everyone else) than check to see what version each unit runs. Unfortunately Pioneer keep a version for every release year and does not update them. The 55 runs icontrol av2, the 61 and 60 run av2012. The new models most likely run 2013 which I would bet have some minor but potentially useful updates. The 2012 version was a nice improvement over the av2.
Build quality, the SCs (not including the 61) have much better build quality than the VSX models. The SC-55 has all metal casing, and weighs substantially more than the 61.
THX, as you noted, the 70 is not THX certified. I have found that the THX loudness plus is the best way to get dynamic sound at reasonable volumes with Pioneers. I use this all the time and find it superior to Pioneers ALC alternative.
The vsx are great sounding receivers, but are not in the same league as the d3 powered SCs. If you are running/resolving speakers the difference will be readily apparent.
Ultimately, the build quality of the 55 won me over. The 65 has the same build and will really feel like a well built high end product.