What is a good video card for installing on my motherboard for adding another monitor to my desktop?

My Dell Inspiron Slim desktop 531s has only one monitor outpur on it's motherboard. I am shopping for a video card to put into one of the empty slots on my motherboard so I can have a dual monitor setup using software like multimon, displayfusion, or similar. I like having the extra real estate to view pages as I usally have more than one browser open at once.

I am seeing many different kinds of video cards ranging in price from a few dollars all the way up to several hundred. I am not a "Gamer" as of yet, but dont rule it out in the future. What is a good video card, check that, what is the best video card that I should buy for around $50 or so? Please advise. I do like the cards that have a processor on them,,,I dont know why, they just look cool . Also, I use 20 inch lcd monitors That come standard with dell computers. They have good resolution and I have it set on highest 32 bit and on 1440x900 pixels