Ok, here's one I think we should have a good look at.
Space Empires, its like a suped-up version of vga-planets and is available on steam and *cough* elsewhere. At $29.95 its not that expensive, alternatively we could go with the version before it which is only $9.95 (assuming it has pbem, which I'm pretty sure it does).
I already have Space Empires V, but have no problem spending 10 or so euro for the other.