First prize would be the G12H Anniversary speaker.
After that, I'd consider a G12M-65 Creamback, G12H-75 Creamback or G12T-75.
I'd prefer not to replace the Blue Marvel with another midrangey speaker like a V30, though I would consider it if the V30 is going cheap and / or I could put the Blue Marvel towards it.
JGP do you have any speakers you'd be interested in parting with?