I'll second the recommendation, Capt Jack. I've been having a lot of fun with, "Gunner, Heat PC." I like the fairly frequent updates and the improvements that keep rolling in, too.
The graphics are excellent, the gameplay is great, nothing not to like, and it is steadily getting even better.
I also play, "Steel Beasts Pro PE" and, "Steel Armor: Blaze of War". They're both excellent in their own way. I'd say that, "Gunner, Heat PC" is worthy of being included in that echelon of armor sims, already. And it's steadily improving.