My old STB Velocity128 has an S-video out port, but it's only a Riva128 chip.
Why do you not want a TNT2? It's just as compatible with all OSes these days, probably just as cheap. Heck, Pricewatch doesn't even list TNT's anymore. And what's wrong with Asus?
The Leadtek WinFast 3D S320 appears to have S-video. Can't find any other TNT cards besides Asus and Leadtek easily.