Honestly, I wish I had a true colour monitor because the prices I get online are half or less than what I would pay at a LQS (if I had one within 30 miles!!!) I am lucky that I have a DH that works in the US and does not mind being my fabric mule LOL.
But back to the origional question--I am usually looking for a specific colour or design, so I shop at least, by manufacturer, and, if possible, by product number. I have found that most online fabric stores are more that readly to give additional info if asked. I added a request for small cream blender civil-war-type print to an order for fat quarters, and could not have picked better myself. They want your business so email and ask questions or even request a small sample.