I remember AnandTech did a comparison, but it was an article a few months ago.
http://www.anandtech.com/show/6877/the-great-equalizer-part-3/2
At the current time, no. I mean, sure you may find that S800 can handle x amount of memory bandwidth compared to y bandwidth of an x86 chip. But what good would that comparison be for?
I believe a high end SOC is as fast as a low end desktop CPU.
Hardly. ARM isn't THAT good yet.
http://www.anandtech.com/show/7314/intel-baytrail-preview-intel-atom-z3770-tested/3
The higher clocked Snapdragon 800 and the new Intel Bay Trail processors are fairly close in Android, and Bay Trail is around AMD A4-5000 (Kabini) performance, roughly equivalent to a Core i3.
Granted, Bay Trail should be significantly faster than the ARM-based processors with Windows or if they have been optimized further since then, but mobile chips aren't far off from the lower end desktop CPUs.