It does not only have to do by your graphic card, also your processor, ammount of RAM, the speed of your RAM, and if it is AGP 8X or PCI-e 16X connection. And a littlebit what kind of motherboard you have.
If that 9250 was your standard card when you bought your pc, it is probably AGP 8X, and a very old computer.
So it is not like you can set everything on high now, because your computer is not powerfull enough.
And why you can probably set everything on medium-high on open see, is because the computer online needs to create waves and thats it. No buildings or landscapes, or other ships. (exept some large cargo ships moving somewhere in the middle of nowhere).
What i am trying to tell you is: You can set the graphics a littlebit higher, but not that you will see a lot of improvement, because the 6200 is also a very old graphic card. You need to upgrade everything on your computer (is what i think) if you want to have everything running smooth with SS2008.
I suppose we dont need to discuss this anymore.
Regards
Niels