I use a Galaxy 8500GT 256MB DDR2 PCI-E 16x and I'm quite happy with it. Got it for Rs. 2.75k in March 2008. It idles around 49 C. There is quite a lot of difference b/w 8400GS and 8500GT. A 512MB 8400GS is purely useless. Don't waste your money on that.
If you want the card for multimedia 8500GT suits fine. You can also use it for casual gaming. If you are a "so-so" gamer you could consider 8600GT. With prices falling, you can also look at 9600GSO for 6k if you are into gaming.