the V30 is WAY more efficient than the GB. i'd think the GB would get lost. there are other speakers that probably complement V30 spectrum better, like the G12H for example.
and yeah, like he said you have to watch the ratings when you mix in low watt speakers. even the G12H will only give you a 60W 212 cabinet.
though if you're really into the GB idea, there are higher watt and higher efficiency GB inspired speakers by makers like Scumback or WGS (to name a couple). likewise for G12H and really all the classics by Celestion, Jensen , etc.