Had to be the 5600 ultra. I bought one of those from a computer fair back in 2003 I think it was. There was me thinking 'I got a billy bargain, its an 'ULTRA' graphics card. Errr - NO.
I installed DOOM 3 & even on the lowest settings it was a slide show.
The second was the first Nvidia card I bought with Native HDMI when I was my early days of dabbling with HTPC's (2007/8) a 6600 or 6800GTS IIRC. It made more noise than a Jet fighter, which made watching films (its main function at the time) a complete waste of time. I kept that card for a few weeks tops. its replacement was a 3870, I think it was one which needed an ATi DVI to HDMI adaptor, much better card for said HTPC use. I still have said adaptor lying around in my PC odds & ends box to this day.