Then wire it up to a L6-30 Outlet
Depending on your voltage you will get anywhere from 5-5.7kw
Very close, but you want everything rated the same that way devices such as breakers can do their job and trip if needed and outlets can do their job and handle the amps that go by the breaker.
You should consider using the existing 2 pole 30 amp breaker and then use the l6-30 outlet. Then go on ebay and buy a used PDU, make sure it is rated for 240 volts and 24 amps.
https://www.ebay.ca/itm/HP-Rack-Mount-24A-200-240VAC-1P-Core-Module-PDU-EO4501-417580-D71-228481-002/401426932271?hash=item5d76e8e22f:g:sFsAAMXQwKdRfsDx
With the outlet ratings on this PDU you should be able to run 3 S9's with the numbers you provided. but they would each need to be on their own PSU because the PDU outlets can only handle 12 amps and that would be close.
Good luck