Geforce GT 640

picture quality is rubbish? do you mean the resolution is different?

Yes, please elaborate on your issue...

Screen resolution is ok but internet streamed Netflix and Youtube video's are grainy, fuzzy, etc.
Basically, would an Intel system get better streaming quality than an AMD system?

No, streaming video quality would be the same if you are using an Intel processor as with an AMD processor.

I do seem to remember that AMD's newer graphics cards offer video quality enhancements to some online streams, maybe that is what you are seeing.
Most likely though, it is just intermittent bandwidth issues forcing your video stream to reduce quality.

So how do I overcome that issue to get good quality?
On the other hand, should I just get an AMD HD 7770 card with a new Intel system?
I'm thinking about returning the AMD system as there are a few other niggles with it!!

If it is a bandwidth issue, there is probably not much you can do against it (other than upgrade your plan if possible).
Simple steps like stopping any downloads, Windows updates or any other streaming apps while watching videos may help.
Streaming off peak hours will probably leave more bandwidth available to you as well...

As to exchanging your entire system, that is entirely dependent on how you use your computer.

To begin, I think using your current 3870K with a nVidia 640GT makes no sense.
The 3870K's greatest strength is in its excellent IGP, the 6550D.
Using this processor with a dedicated GPU not to much more powerful just seems like such a waste.
That said, the 3870K is an excellent all around processor suitable for light gaming and general workloads.

On the other hand, an Intel build, depending on the specific processor, can be quite a bit faster in highly demanding tasks.
Coupled with the much more powerful 7770 it would also be a much more capable gaming machine.
With all the increased performance, you will be paying quite a bit more and using quite a bit more energy.

So, it really comes down to what you plan to do on your computer.
For standard usage and light gaming, your current AMD build less the 640GT is quite good.
If you want a gaming build, exchanging for a more expensive Intel build is a compelling option.

Interesting what you say about the bandwidth issue in that I also have a Dell XPS 8300 with a Radeon HD 6450 card and never had problems with it and the picture quality is reasonable. However that machine is intended for other uses and so I want to keep my day to day personnal antics off it.
This new machine is for day to day use which involves alot of web usage and so I wanted it to have better graphics quality than the 6450. However, at the moment nothing is competing with the 6450, not even the 6550D!
Cheers

Have you ever come across issues with the mouse cursor and web links intermittantly freezing for a second or so when clicking on links, is this something to do with the graphics card or another part of the system?