Still haven't heard a CSP+. Maybe someday.
I haven't heard the Taboo MKIII, but I didn't like the Taboo MKII with HD800 at all... so I can't comment. I'm not optimistic but time will tell. The Taboo was designed for lower-impedance cans.
Decware recommendation is using the CSP+ OTL/preamp with the HD800. Beautiful match, especially for the price.