Hi,
I have an HP a1640n and I want to put in a graphics card. Any suggestions on what card to purchase in the $100 or less category? Also, will I need to upgrade my power supply for the new card?

That computer

HP Pavilion Media Center a1640n Desktop PC has a PCI_E X16 slot.

High end cards would require a larger PSU but not ones' around $100.

You will find the low end for these cards is $100>$200.

High end is around $600>$700 and up.

A lot to read here:

http://www.google.com/search?hl=en&r...+cards&spell=1

Also here is a list from Newegg (who offer a wide variety):

http://www.newegg.com/ProductSort/Ca...-Video-Devices