Unless you need the enhancements in 11.x, I would stick with Solaris 10.
For hobby use, 10 should do everything you need and also supports a
graphics card, which afaics, 11 does not. Find something like an XVR300
and suitable kbd and mouse and you have a usable Gnome 2 based desktop.
Quite useful if only to allow multiple shells open at once. Xvnc is
included as well, though you need to dig to find the setup info, as
it's not well documented.
As for firmware, you need a support contract to get that, but I would
try it with existing firmware to start with. A dealer may be able to
help with firmware, but never needed it here for hobby use, original
has always worked just fine...
Regards,
Chris