I also got my 60 gal unit on sale from home depot. 220v is the way to go if you can swing it, you just can't get much more than around 5-6cfm @ 90psi out of a 110v unit(this sounds like about what yours was, back in it's day). Just can't make enough horsepower on a practical 110v unit to spin a large enough compressor. The entry level 220v 60 gallon units put out about twice that cfm, but have the tank capacity to run a larger tool for a long time. A small tank one like yours will run out of breath a lot sooner, but regardless, if you've got the proper line size, the tool should work fine at first, just after an amount of use, tank pressure will drop because the compressor can't keep up. I don't think you're going to be runing a DA sander with what you've got, even if you add in an extra tank. The smaller compressors work decently for intermittant use like an air nailer, and light air ratchet/impact wrench use, but not so good for constant output devices like angle grinders, paint guns, DA sanders, etc. Even with the add-on tank, use will be intermittant as you'll have to stop and wait for the tank to fill a bit so you can gain power back. The extra tank capacity gives you a longer usage time, but also a longer refill time.

I was in the same boat as you, did not want to spend all my dough on a new compressor, so I kept using my tired, leaking 13gal 110v unit until I finally just could not take it anymore. If you use tools made for your compressor's size, they work fine, but when you want to do more than your compressor can handle, it get irritating, very quickly. Lol, just try taking off a cylinder head with your impact and a smal compressor. Last time I got 6 bolts off before I just ran out of power and had to just put the gun down and let the 110v unit refill. No more of that for me.