You wrote: "We went back and forth with Centerpoint Energy and the only thing we could get was as follows: New underground 400A service from the Transformer to the house, terminated to a new 320A meter can (80% load). From there the load is split between the home (still 100A) and shed (225A). The cable that feeds the shed is the same size as the one feeding the house (capable of 400A) but the panel they installed is only rated for a certain size. I may have him come back out once I have some ASICs pulling more juice to see what other options we have."

I am in Houston too and wanted to go from 200amp service to 400amps.  Centerpoint said I would have to pay for a new transformer (the current one serving 6 houses is 50 kVA), pay for the concrete pad that goes under it, pay them dig up a bunch of my neighbor driveways, their landscaping, repairs to same afterwards, etc.  The total cost was nearly $30k!!  did they charge you too?  how much?