Getting your frame sandblasted is good value. You have to compare it with the time spent trying to get all of the paint off with chemicals, your electric drill and brushes, sand paper etc. You can easily blow a weekend. Getting a complete frame and a box of parts sand blasted has never cost me over a hundred bucks. I have always gone with RCJ but that's just because I know one of the guys there. Bull Dog has a good point about Prism; they helped the club with our R5 project.
With regard to powder coating your frame afterwards, I have done it. The quality and durability cannot be beat. However, I have no plans to powder coat any frames again in the near future simply because my projects are never finished. I have spray painted my own frames with proper two part automotive paint, and frankly, for any of my projects (which are all done on a Spartan budget), I'm going with spray bombs. My GS650 frame was done with automotive paint. I then spilled brake fluid all over it and messed it up. My repair was a spray bomb. My drag bike was about $20 worth of spray bombs.
A high end restoration would be worthy of powder coating, but a budget bobber .... your call.
Peace & Grease, Dennis