This server is running an extension (you could call it a mutator, but it is so huge that should be called Mod...or safer as it is - an extension :D)
If you are fond of tanks fighting under DH Engine you should be in heaven - there are quite a lot machines added to Axis and Allies side; more - there are Russians with their stuff!
http://www.youtube.com/watch?v=BHl4DQRequM
The project is still being developed so for being up to date join the Steam Group:
http://steamcommunity.com/groups/RealPanzer
The server for now is 30 slots of capacity. If you are having fun there - consider donating - I'm sure they could bring a few slots more then ;)