[SpiritWarrior]

You'd need a card that can render HD and one that can render it well. Some on the low end do technically, but not very well and can result in a signifigant performance hit. Movies etc. aren't a big issue in this respect, but games are.

If you are attached to what you have now, upgrade the ram (the amount you have is fine), the mobo and the video card. Make sure your PSU can handle the new card. There are also low-power consumption cards out of current generation models, requiring less PSU leverage than normal. May be something to keep in mind. Again, if you're updating the mobo (to cater to your dual core switch), ram and card...and possibly the PSU, you're far better off just building a new one, and selling that for $$ as a second rig. This will, in turn, fun your new one. If all this is being changed there won't be much left to keep other than the casing and fans really. Just my thoughts on it.