My GF graduated from the interior design program @ BCIT a few years ago.
Here's how I would rank what you need:
1. Screen size & Resolution
2. CPU
3. GPU
If weight or size is not a concern for you get a 17.3" screen and the highest resolution you can find. Small and light is nice and portable but trying to use AutoCAD/sketchup/revit/vectorworks on a 13.3 or 14" screen?

i5 processor (i7 will be out of your price range)
Something better than an integrated GPU.
Here's what I would take a look at:
Option 1:
http://www.futureshop.ca/en-CA/produ.../10225906.aspx
Screen: 17.3" 1600x900
CPU: i5 3210
GPU: 7670m
$699.99 (exclusive of taxes, unfortunately)
Option 2:
http://www.futureshop.ca/en-CA/produ.../10232361.aspx
Screen: 15.6" 1366x768
CPU: i5 3210
GPU: GT630
$599.99 (exclusive of taxes).