I've been in the mood for a space combat/commerce game lately as well, and the X3 seems to be the epitome at the moment. It does sound like a pretty intense learning curve though from all I've read. But for $20 through Steam, I may check it out.
I did the demo for EVE a while back. I like the concept, but the controls killed it for me. Personally I want first person control of my vehicle during combat. Clicking orbit>attack wasn't my cup of tea.
The reviews of Darkstar One are OK. It sounds pretty much combat oriented though, the trading is pretty skimpy sounding from what I read.