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=N82E16814102906
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-Multimedia-Player/dp/B002LTRCRW/ref=sr_1_2?ie=UTF8&qid=1286765822&sr=8-2
But there are better ones for a bit more that you can network with your PC.