By the sounds of it the engine is probably capable of bringing any of today's PC's to their knees .... 48000 troops would be hard for any of Today's PC's to handle

Once i get my hands on the game i'll let you know how many people i can get in a battle (at a decent fps) on my rig, as its fairly high spec .... although i suspect people with high end AMD64/FX rig's would fare much better

P4C @ 3.7ghz
1gb DDR 500
6800 GT