There's a free Supreme Commander 2 demo on Steam that you can play providing your PC meets the listed system requirements.
Publisher Square Enix released the demo alongside an announcement that Supreme Commander 2 will support Steamworks - Valve's handy set of developer tools.
Steamworks has been a bone of contention among digital distributors in the past. Direct2Drive, Impulse and Gamersgate all refused to sell Modern Warfare 2 because the game used Steamworks. Games don't come more high-profile than Modern Warfare 2, which suggests those sites may also boycott Supreme Commander 2 if their grievances haven't been addressed.
The Steamworks tool inevitably pushes players towards Steam at one point or another, no matter which digital distributor they bought the game from. But that shouldn't matter to you. And Valve doesn't care.
All that really matters is Supreme Commander 2 and the pedigree of developer Gas Powered Games. The first Supreme Commander was great, and the sequel is shaping up interestingly.
Check out our recent hands-on impressions of Supreme Commander 2 while your demo downloads.