Yeah . . . I am pretty sure the numbers wouldn't add up to upgrade barring some unusual find. Mine's a 6HP 33-gal Craftsman (8.6 scfm @ 40 psi / 6.4 scfm @90 psi) that I scored on CL several years back. It gets the job done, just takes some time. I have no interest in doing winterizing for anyone other than myself. I literally use that compressor once a year for the sprinklers. I have a 15 gal Craftsman (also a CL buy that I bought first) and a little Harbor Freight pancake compressor that I use all the time since it's so portable.
I hear you about upgrades. If I happened across a nitro methane powered compressor for a song, well... I might just have to have that. Wonder how many feet of hose I'd need to hook up the surrounding blocks to make it worth firing up & the subsequent rebuild.