Hi Ron,
I really suggest that you do NOT get the Line 6 Cab.
I have a Vetta Combo, as well as the HD, and the Combo's Celestion C90 speakers (same in the 4x12 cab) are an early attempt at FRFR,
and they do not sound good. Using a different, well-built 4x12 cab: Marshall, Diezel, Engl, Mesa, Orange, etc... will work excellently with the Vetta HD.
I would also suggest something other than Celestion V30s,
but rather 75s (G12T75) or even 100s (G12K100) speakers will give you the thump and the clarity you need to sound rich and full with the Vetta.
To see which version Vetta Firmware you are running, Press the System Setup button, and scroll with the Knob to the 4th Page.
It will tell you what version software you are running. If it's not Ver 2.50, then go the the Vetta Group at Reddit,
and you can download the Ver 2.50 Firmware.
You'll need a M-Audio Midisport Uno to connect to the amp ($50 on Amazon)
and download Midi-Ox to load the firmware into the amp.
Then you are finished, and off and playing!
Will