New-ish Computer Need Graphics Card Help.

Just had to get another computer...and while I plan on buying a higher end computer soon enough, (this one was a 150 dollar cheep quad core.) I am having trouble finding a good graphics card for this system as my old one is too large for it. I currently have 4 gig memory and a Dell Inc. 0PU052 motherboard and a quad core cpu. the casing is an optiplex 755. I need a graphics card that is somewhat high end, but at least under 300 dollars....and small enough to fit within this case. An hdmi port on it would be nice but the white connection is good as well. Most sites I looked at, I could not find sizes on the graphics cards but i did manage to find a site that listed what size i actually needed for my case.

• Height 4.376"
• Length 6.6"

Thank you for any help I can get.