Would that fan for the 5870 that you linked us to off Ebay work on the 5830? Sorry for the bad day...I'd say throw that 5870 from Z in there (the one you had in the Hydra rig) and at least you'll have something crunching that way...let me know if we can help you on the parts end of things. I honestly don't know if it's worth the $$$ for an aftermarket cooler on anything lower than a 5870, but that's just me looking at it from a utility cost per credits ratio. Obviously fixing what you've got is better than buying new most of the time on limited income...
One last thought - could you modify one of those sweet coolers you had on your old nVidia 8800 cards? I seem to remember you had 2 older nVidia cars with some hog aftermarket coolers on them. I know your skills man - you have mad modding in the blood! Maybe you could get one of those to work on your 5830?