Hi mccoady, I have to say this is one of those cases to say 'if it ain't broke, don't fix it". Your 8500GT is a very weak card, BUT I'm pretty sure it can do GPU acceleration when it comes to video decoding. I have a 8200GS that can do gpu acceleration, that I keep as a back-up.
I have to say on the other hand that a newer card will probably produce slightly better colors and a slightly cleaner image. So here is a suggestion for an inexpensive card that has HDMI output for your HDTV. This is not a gaming card, but it can do basic games. If you want to spend a little more and get a card that can play some modern games we can give you some suggestions.
PowerColor AX5570 1GBD3-H Radeon HD 5570 1GB 128-bit DDR3 PCI Express 2.1 x16 HDCP Ready Video Card $40 AR FS
Because your old card is Nvidia and the new one will be AMD, you should uninstall the old video driver and use a free program called Driver Sweeper.
First uninstal the old driver, don't reboot, run driver sweeper to remove the old Nvidia video drivers, then shutdown the PC, unplug the power, install the new card, then when you start the PC you can install the latest AMD video drivers.
I realize this video card may not fit the required GPU that the software wants, but it is plenty fast for doing video playback.