It seems I don't need aux/realemu and aux/vga at all to boot rio, it can
run with monitor=vesa and vgasize=640x480x8 in plan9.ini. I still haven't
found out how to run in 1024x738 with vesa, through, will check if it can
run at least at 800x600 with the vga command as you said.

BTW, there are two things I have detected in Plan 9 that I love: the
ability to copy and delete text in rio like if it were a simple file (much
like the rest of Plan 9) and no CapsLock support (why other operating
systems still support CapsLock? Seriously, it should die).