Okay, Terry, first thought that came to my mind--have you tried ikea's website? You can get general measurements of the sizes of furniture/shelves you'll need from their website. Perhaps draw it out on paper how you want it to look as well.
IMHO, I wouldn't recommend an entire table top dedicated to your computer and projects. Why? Because if you suffer from FSS (aka Flat Surface Syndrome!), you'll eventually cover the entire tabletop with stacks of things...papers, projects and that'll leave you frustrated because you "knew it was here a minute ago!"
How do I know this? Welcome to MY world! I have ADD. My mom and I share a room (10x12ft) where half of it is her side for her computer armoire, and desk. The other half HAD my 8 foot table in there. I took out that table, which was really collecting things and leaving me less room for working, and put in an architect style desk that has a smaller 'footprint' in the room. I also put up some shelves beside my desk for baskets. I am making use of rolling drawers, and even though it's less space, I feel a lot 'better' because I'm not so overwhelmed by things piling up in there. (I create greeting cards for friends/family.)
Ikea has a 'planner' for offices, kitchens and bedrooms. Have you downloaded & installed that program from their website? http://www.ikea.com/ms/en_US/IHP08/IKEA_Home_Planner.exe that might help you figure out which pieces would work best in the room. Good luck!