Graphic card & projector & other

Hey. I hope you are well.
I am thinking about buying a projector. After long consideration I have
ended up on either the Infocus sp4805 ( with DLP) or the Infocus
sp5000.
As the situation is now, I have my DVD, VCR, TV and old CommodoreC64
connected to my PC. I want to connect my projector to my PC. And get it
all on the wall. At approximately 180cm x 101cm (1cm=0,39 inch  ).
Now I have some questions:
1.) What is the advantages of DLP? (Or the drawbacks of not having it!)
2.) My screen runs in 1024x768. But the sp4805 has a maximum resolution
on 800x600. Will that be a problem? Will I then not be able to run
PC-games in 1024 on the projector?
3.) I was told that the strength of the graphic card is vital for the
quality of the projected image. Right now I have an Geforce4 ti 4200.
But do I have to upgrade? If I upgrade I will have the opportunity to
connect the projector via DIV instead of VGA; I plan app. 10 M cable.
Will I win a lot on DIV?

---Which of the projectors would you consider the best? Or maybe you
even have an alternative proposal for a projector based on my demands
and needs?

All the best, Simon Schmidt