Move Unwanted Office Items into the Garage Second
Now that you've gained a little room in the garage for your "stuff", you can begin moving it there. Before you do though, seriously consider getting rid of old printers you don't use, scanners you don't need, and even old computer towers that aren't quite dead, but will be soon. There's no reason to store items you won't need later.
With that done, consider what needs to be moved out of the office. Box items together in see-through plastic bins if you can afford them, and write on the outside what's in them. You can have one large bin for old tax papers, one for old contracts and reciepts, and one for cables you only need to access rarely (Ethernet, Coax, USB). These bins, once filled, can easily be moved and stacked, so they take up very little room in the garage.
Now you can start moving the larger items. If possible, purchase shelving (or free an existing shelving unit) to hold only office-related items. You can put extra paper here, old computer towers, photo printers you rarely use, and similar items. While you're in the zone, take a look at what's in your office that's not office-related and move it too. Just because that's where you've always stored the cat food, the extra linens, winter coats, and the like doesn't mean that's where it has to stay!
So spend a day getting organized; trust me, you'll work better, be more relaxed, and produce better work! There's nothing like a clean office to inspire!