Changing GPU

I have an old dell xps420 Core 2 Quad 6600, 8GB RAM and a 1tb drive desktop ( http://www.pcpro.co.uk/reviews/workstations/162588/dell-xps-420 ) and want to add a hdmi video card to it - not to play games just for hd video to playback stream sports - can someone recommend a good but cheap GPU for this, one that will be compatable with my computer. 

most hd 5450 have HDMI and are quite cheap, though newer low end cards are better for video now.

http://www.newegg.com/Product/Product.aspx?Item=N82E16814121439

Thanks. Can i just add this card to my current pc and use the hdmi for Sound output only or will i have to replace my old card with this.

I recomend an AMD hd 6450 (same price as the 5450). Silent fanless version isnt bad at all. Maybe a nividia 520 I think they have a silent version too. Lots of different brands/colours to chose from for the 6450 if it matters at all.

You can use the hdmi sound or what your using now, whichever you prefer.  When I put in an AMD card in my pc it automaticly asked me in a window when i first booted up or right click the speaker icon open volume mixer and the chose what you want from the first drop down menu. Or its right click playback devices and pick what you want, i forget but i think both methods work. 

Thanks for the replies. So if i plug the second gpu in i dont need to do anything else it will be ready to go? As i have read online you have to 'trick' your pc into thinking you have one gpu or there will be issues?

You mean you have integrated video and you want to use your new card? Just plug the cable in the new card and it won't use the igpu (or else just disable it from bios).