You mentioned you do not want to sell your cards as singles but you can make a significant amount more than if you sold your collection in bulk. This is especially true if you have cards valued over $50. For a minor investment of your time, you can get anywhere from 80% to 95% return on the value of your cards if you sell as singles.
Selling in bulk is easy but you have to know what you want to get before you go down this path. If your collection is uploaded to deckbox, export the CSV file with the price information included. Then open it in excel and total up the all the mid and low prices in the file. Multiply the mid and low totals by 60% and try to find buyers that will pay an amount between these totals. If you want to find a buyer fast, you can try posting your sale on MOTL and MTGS also. Ebay is also fast way to get rid of cards but you will lose an additional 15% in fees.
If you are going to deal with someone online and your collection is huge. You might want to invest is some 5000ct. cardboard boxes (the big 5 row boxes). It would also be a good idea to take some high quality pictures of some of the valuable stuff in your collection so you can post pictures. I use dropbox to host any images of my cards.
The easiest way to sell bulk is to wait until there is a large tournament (SCG open/GP) in your local area and take your collection to one of the dealers. They will give you a non-negotiable lowball offer but will usually take anything you have.
Hope these suggestions help.