What's coming down from his panels aren't 12V, they're likely strings somewhere in the 150-300V range. Even individually, larger panels like this individually are above 25V themselves. Not to mention the solar power isn't constant enough; you'd be varying input voltage constantly. You need the inverter to smooth it out and make it a clean and stable power.
Hack some cheap server PSUs to perform MPPT, then parallel the output with unmodified server PSUs to get a constant voltage. Hack the load share to give preference to the solar PSUs, with the normal PSUs supplying the remainder. It will take a lot of electronics knowledge to do it.