[tr4dude]

the cfm rating on the cabinent is how much air you will need to run it constantly at 90 psi so for most jobs you use it for if you get say a husky 60 gallon at home depot for about $400 rated at 10cfm at 90psi it will put out enough air to meet most of your needs. make sure you do not get a oiless compressor, they are loud and will not last long using it for sandblasting.
my first compressor was a sears professional 33 gallon oiless model, with a 5hp motor but running hp was 1.7hp, so the 5hp rating was what the motors maximun developed hp would be if it was brought to a stop turning the compressor. it was rated at 15 amps on 110v power. stay away from this type of compressor. i would sandblast for about a minute or two and have to wait for it to build pressure back up to continue. a true 5hp compressor will be 220v and rated at 20 to 23 amps and the pump will be belt driven. these type of compressors put out alot of air and are much more quiet. and as a rule of thumb buy the biggest baddest compressor you can afford, you will be happier in the long run. i bought a champion 80 gallon 5hp that puts out 23cfm and paid about 8 bills used, it puts out more 4 times the air of the craftsman compressor i have and is twice as quiet. and i suggest to stay away from kobalt to at lowes checked those out and looked ok but all the ones in the store were leaking oil and the plasting hose to the tanks was said to blow on the big model. check the craigslist for champion, quincy or ingersol rand, you can find deals if you look even check at the auctions.
hope this helped. good luck