Bob,
You really need to take a close look at what types and/or sizes you will truly need. You need to look at three things.
First, what do you plan on using them for. What will the common sizes be of what you plan to blast? Mostly big, mostly small or a mix.
Second how much you plan on blasting. If you are only going to blast a few things months or years apart, rentals may be a better option.
And third, and maybe most importantly, can your present compressor handle the volume that either the pot or cabinet requires. Blasters need a lot of air. I have an 80 gallon vertical compressor that I give a real good workout when I am blasting. You would likely be disappointed with a large blaster and a small compressor.
I have a vertical blast cabinet that I use a lot. Mostly it seems for things that have nothing to do with my restoration. Lots of small stuff that get rusty seems to pass through that cabinet on their way to fresh paint. But no matter what cabinet you get, my only advice is to seal every seam with silicone as you assemble it. That will save a lot of stray dust problems later and save on media.
As far as the pot is concerned, I used to have a small gravity pot that was ok for small stuff, but I like my 20 gallon pressure pot much better. It seemed like the gravity pot I had was limited on the adjustments I could make to the flow. It always needed full pressure to work right. Don't get me wrong, there is nothing wrong with a gravity pot. I just like a pressure pot better.
I have blasted things from as large as a 275 gallon fuel tank to vehicle parts with my 20 gallon. The only advantage a larger pot has over a smaller one is you don't have to fill it as often. A 10 gallon would do a great job, and I think the air consumption is about the same either way.
