You want a continous flow dryer, brand should be the one with not necesarily close, but fast efficient service (call 24 hours).

If you want to dry 500-800 bu per hour, youll need a big dryer to heat and cool, not so big to heat blow through and cool in bin.   Our Delux dryer does 850 hr heat / cool then to the leg.  We use to cool in bins, but built bigger bins and are happy with the system so far.  Only problem is in wetter corn it slows the harvest.   Now with 17-18 % corn we can dry to 14.5-15 moisture around 40,000 in 24 hours.

Remember all "rated" dryers depend on outside air temp and humidity.   I believe dryers that heat upstairs and cool downstairs use less fuel basically because its pulling the heat out of the corn down stairs.

Just some thoughts and opinions.

Have fun shopping..........Be prepaired to spend big bucks, but reap the rewards down the road!!!