To be honest, Yes you did wast 100dollar. :(
If you don't know anything about it then do yourself a favour and check some reviews on the net.
If you still can return your card do it, say that it was a mistake.
I wouldn't even recommend the 5600 to anyone.
I think the best performance for the money would be a Ti4200(128MB) for you.
(very good cards are not cheap)
It will still not be very good but you should have about twice what you have now.
But if you are willing to give a bit more money so you can also play DX9 games (like HL2) then a 9600Pro is probably a good choice. The LOMAC performance won't be much different than the ti4200 though.
The image quality will be better with the 9600Pro.
The best card you can get at the moment is the ATI 9800XT but very expensive.
The second best choice is the 9800Pro.