Video card questions for PCIE

I am thinking a new video card will do me some good.

I currently have an on board NVIDIA GeForce 6150SE nForce 430 with 128 MB

There is an available PCI Express ×16 and I have found no version number, so I am assuming version 1. Also, in what I found in research, my system was built at about the same time as version 2.0 was released All I can find in the online documentation is:

This is the PCI Express ×16 connector on the motherboard. It is used for graphics add-in cards. PCI Express ×16 offers up to 4 gigabytes per second (GB/s) of peak bandwidth per direction and up to 8 GB/s concurrent bandwidth.

If I get a video card that is PCIE with a version higher than 1 are they backward compatible?

I tend to use Office and other applications, surf the net do some tinkering with video and image editing and watch TV in Media Center. WMC currently consumes 35-45% of my CPU when I watch TV, Netflix or recorded shows, but only about 5% recording them if I am not watching anything... I get some occasional issues with video playback stuttering, and it seems to be related to when the CPU usage spikes , so I assume I would benefit from a slightly more powerful video card as it could remove cycles from the CPU and/or not access as much shared memory.

Based on the above, are there any suggestions for a video card that might help me? I need a single width card due to the tuner card being in the next slot, any suggestions? I don't think I need anything very powerful, but more than I have might be beneficial.

Any comments welcome.

Yes.

Even if you have a PCI-E 1.0 slot, a PCI 2.0 GPU will work in it.
They are indeed backward compatible.

if not a huge gamer:Maybe something like a HD5570, or HD4770 would do well for you. Depending on what you want to spend.
These run around $85 --> $110 and would do great for Video/photo editing and some light gaming even.

Unless you want to stick with Nvidia, but Im unsure off the top of my head what thier equivalent would be.