Looks like your pretty limited with the 300w PSU you have.

Look for these chipsets - GeForce 210, ATI Radeon 4350, Ati radeon 4550. There maybe more chipsets. Here is an example of a Geforce 210 -

http://www.newegg.com/Product/Produc...82E16814121348

Really upto you if you want to run a maxed out 300w config or a lower consumption setup and have some headroom. http://www.newegg.com/product/Catego...eId=199#topic4.