Okay, I have a solution to my problem. I phoned the electrical supplier I usually deal with and told him what I wanted. He asked, "What company are you with?" I told him that this was for a home project and then described what the project is. You'd be surprised how co-operative men can be when you tell them you're building an elaborate brewing rig.
So then he asks, "I understand this is for yourself, but where DO you work?" I told him, and since it's a major company well established in the electrical field he said, "Well, that will save you quite a bit!" I guess I get the company discount. No conflict of interest if I disclose that the parts are for personal use, right?
So the bill will be around $220 for a new 60A Stab Lok breaker that feeds a Square D spa panel with a 60A GFCI breaker. The panel apparently has capacity for two more two pole breakers. I'll need to buy about 20 feet or so of 6 gauge cable and conduit to hook it up. Also, since the panel can only accommodate two other two pole breakers, I'll have to feed my miscellaneous circuits off another single pole circuit. I already have an in-line GFCI for my March pump.
I'll be picking up the panel later this week.