unless the room is pretty small or you like to listen quite softly, 300b is ruled out
cav 45 vs rocket88 a matter of taste, both are on the tubey, rich slow side, treble will be sweet, midrange will be luscious, but bass will be bloomy and little mushy
rocket 88 maybe a touch better in that regard, but cav45 may have better resolution in the treble and mids