1. I'm assuming I need a hdmi - DVI converter.
2. I currently have a nvidia graphics card that will run my first 2 monitors. Do I need to stay with nvidia? I've been reading that ATI will be better for movie watching.
3. I'm thinking of getting an external tb usb 2.0 hd for downloaded content. Will it make much of a difference watching content off an extranal drive over internal?
Also, can anyone recommend a graphics card maybe under $150 that will be able to watch movies nice and smoothly? 100% watching movies and tv shows downloaded and will be buying a blu ray drive soon after to watch best quality movies. My current graphics card will be used up by 2 monitors and there will be no other purpose for this graphics card then just watching movies.
Does your motherboard have a second PCIE x16 slot? If not you'll either want to get a second card that uses a regular PCI port or replace your current card with an HD5000 card as those support 3 monitors on their own.
If you go for two card I would stick with Nvidia as running two different sets of video drivers can cause headaches. If you would prefer to use one card then this is a good option; http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Otherwise you can get any HD5000 card with a displayport out but you'll need to buy an active display port adapter for about $25-30.
That said are you sure wouldn't be better off just getting a digital media player for the new tv? I've used this thing and it works great; http://www.amazon.com/Brite-View-BV-6000P-1080p-Multime...
But there are better ones for a bit more that you can network with your PC.
For gaming the HD5770 is approximately 50-60% faster than the 9800GT your system has now and has more current features like DX11. If you are talking about using the card to game on all 3 monitors at once it is a lil weak for that but if you are willing to use modest settings it should do ok. Might be awkward because the tv will be much larger than your other monitors though so the images won't match up.