You've got a newer video card but not top of the line. GTX 580 seems to be top of the line however there might be a 590. Unless your in the 80's or 90's with Nvida, your only getting a card with higher compatibilities with new games. Need to spend the extra few hundred for 'perfection'.
Regardless it is still a very good card (appears you spent about $350 on it) that I'm sure will serve you very well for a very long time and I don't think it is worth spending an extra $200 just for those extra things to show. There is far more about DKS than just graphics!
Also Nvidia releases driver updates that helps improve performance on their cards about every month.
www.majorgeeks.com is a great place to keep track of driver updates. Just make sure your getting the Nvidia video driver updates not the mainbaord ones like some guy did a while back.
In a few years from now I'm sure you'll want to play this again and will have a card that will handle DKS perfectly.
About the 32bit issue, this game has been in production for a long time (they started Ego Draconis 6 years ago) so the upgrade to run 64 bit might have only delayed their product even further. Regardless I'm sure DKS will be their last 32 bit project unless they want to push something out by next year with the same game engine.
EDIT:
can't find a GTX 590 for sale but reviews had some numbers that will give an example of what I was going on.
NVIDIA’s GeForce GTX 59x boasts a TDP of 375 W. That’s massive when compared to the other GPUs – for example GeForce GTX 580 has got a TDP of 244 W.
TDP: The Thermal Design Power or TDP in short, is the maximum power consumed by a device (graphics card for example) under normal / regular use.
And a futuristic GTX 650 (when ever it will come out) will be more compatible than the 590, but about as powerful as what you have now.