hi noah
you should be ok with a card such as the Palit GeForce GTS 450 Sonic 1024MB GDDR5 PCI-Express Graphics Card ( http://www.aria.co.uk/Products/Components/Graphics+Cards/NVIDIA/NVIDIA+GTS+450+Series/Palit+GeForce+GTS+450+Sonic+1024MB+GDDR5+PCI-Express+Graphics+Card+?productId=41478 ) ....this is more than enough to cope with world of warcraft and rift and has support for both direct x 11 and pixel and shader model 5.0
from the information you supplied it looks like you are currently using a onboard graphics solution.... the pentium E2220 is actually a processor and not a graphics card..... however this cpu and the card i recommended will work well.. and as long as you have at least 2gb of ram you will be good to go
you could go for a more expensive card such as the GTX460 or the radeon HD5830 however your cpu may not be powerful enough to get the best out of these cards.... so you need to stay with the budget/mid range cards which are more suited to your cpu
if you prefer a ati radeon based card then i would recommend the Sapphire ATI Radeon HD 5670 512MB GDDR5 PCI-Express Graphics Card ( http://www.aria.co.uk/Products/Components/Graphics+Cards/ATI/ATI+5600+Series/Sapphire+ATI+Radeon+HD+5670+512MB+GDDR5+PCI-Express+Graphics+Card+?productId=39374 ) .... this is less expensive than the GTS450 and is actually more suited to your cpu...... and its specifications are not that bad considering its £59 price tag
these include a 775mhz core clock and 512mb of gddr5 memory running at a massive 4000mhz ddr effective.... theres also a 128bit memory interface and support for both direct x 11 and pixel and shader model 5.0 ...... also theres 400 processing cores
however more importantly this card requires no additional power connectors as it only draws 69w at full load... and the pci-express bus can supply 75w........
personally i would go with the HD5670... its less expensive and more suited to your cpu and will also run the above games without any problems
i hope this helps noah,however any questions let me know
good luck mate !