First up 3 sets of miniatures rules.
I had always heard good things about Corps d'Armee so was glad to see this available the other two I know nothing about but when has that ever stopped me !
PC game purchase (via Steam) is Field Of Glory II from Slitherine/Matrix
It is a port of the miniatures (although I think 1st version was a more direct port) rule set but with some tweaks for the PC environment.
It has a nice manual (PDF version sadly) but if you have played the miniatures game then its pretty intuitive.
I have only played initial tutorial and set up a 'luck dip' type custom game but quite impressed with this, good solid game play with a host of scenarios and campaigns and of course the custom battles and it sports 2-player/Pbem mode (not tried this).
The animations and battlefields are very nicely done with lots of viewing options including a top down view.
The interface is easy to use and seems to run on fairly low spec.
Here a couple of screenshots from ongoing Gallic vs Roman game showing a couple of the views available.