Have you thought about finding a way to feed the DC from the solar panels directly into the 12V consumers and bypass the two transformation stages?

That could potentially give you another 10 - 15% more net power by reducing losses. I know they do things like that in large datacenters sometimes. Unfortunately, 12V PSUs are still not mass produced and therefore expensive. However, compared to high end consumer PSUs and solar panels, it may be very profitable. You could perhaps implement it by using some properly dimensioned battery bank like an UPS and then add some custom wiring to the GPUs.