You will see a huge difference going from the 3000 (I had one) to the 5800. However, both are old tech. I understand you're trying to fit in a tight budget. The recommendations above are fine, but you could get a very nice mobo for about $50 at Newegg. There are several to choose from, MSI, Asrock, and other mfgs have several models each. http://www.newegg.com/Store/SubCategory ... rder=PRICE
They are AM3 760G boards w/built in video, so you don't need a separate card.
The performance will be a lot better, but you'll notice that compared to the x2 5800, you will use a lot less power and produce less heat as well even if you get a dual core (AM3) instead of the older AM2 cpu.
My son has a x2-6000 and my daughter has a Regor x2-260. Both have similar performance numbers but her computer runs cooler and use less electricity.
Rig#1: Intel i5-3570K, MSI-B75MA-P45 mobo, G-Skill Ripjaws DDR3-1600 2x4gb, MSI-7870 2gd5t/oc gpu, Tt TR2-600w psu, Tt Commander Snow ed. Case, Cooler Master Hyper212+ HSF, OCZ Agility3 SSD 120GB, WE Caviar Black 750GB
Rig#2: AMD Phenom 2-970, MSI-890FXA-GD-65 mobo, 6GB Geil DDR3-1333, HIS Radeon HD6870 1GB gpu, Antec Quattro-850 psu, Rosewill Conqueror Case, Zalman CNPS-9500 hsf, 1TB Toshiba Sata3 HD