Figure the boat can go six knots at cruising speed under power-hull speed for a boat with a 30' waterline is about 7.5 knots, so this isn't an unreasonable estimate.
You say it is 560 miles, or approximately 94 hours of motoring at six knots. You say it can be done in eight days of motoring... which is 11.75 hours of motoring per day, not counting stopping for re-fueling, stopping for lunch, etc. Chances are that most novice delivery captains are not going to be willing to motor in the ICW at night.
Say your boat has a fairly decent size fuel tank and can do said trip with three tanks of fuel, they'd have to stop four or five times to get fuel, since they wouldn't want to risk running out of fuel, and assume getting fuel will take about an hour with everything involved.
So, you're offering to pay 800-1200 for a captain and crew to work about 115 hours over the course of eight days... or less than $4.00 an hour if there are only a captain and crew. Hmm... yeah, I think you're going to attract a really qualified captain and crew.
Of course, this doesn't account at all for adverse currents, bridge delays, weather delays, or mechanical problems. I seriously doubt that a trip of this length will have no mechanical problems. Of course, the captain can run the boat at hull speed, and put a lot more wear and tear on the transmission and engine, and burn a lot more fuel, but he might shave a day off the trip.
IMHO, most sailors, who would be interested in doing this trip for the experience, not the money, would probably prefer to go outside and sail the boat, rather than motor up the ICW. However, you've already made your preference for a motor delivery via ICW known.