First are you sure it is the amp? Have you tried any other sources? Have you tried things like taking the cable from the side that doesn't work and put it in the side that works? Moving the tubes from the right side to the left and check bias.
As far as tubes they will make a difference. Big difference - Maybe. Either for the better or the worse. Usually better. Some tubes are warmer sounding than others and some are very linear. The only way to know is to try them. Since I'm not familiar with that amp I will not make any recommendations. My Octave V70SE takes many different types and I will say different brands of the same type will be different sounding.
Good luck
As far as tubes they will make a difference. Big difference - Maybe. Either for the better or the worse. Usually better. Some tubes are warmer sounding than others and some are very linear. The only way to know is to try them. Since I'm not familiar with that amp I will not make any recommendations. My Octave V70SE takes many different types and I will say different brands of the same type will be different sounding.
Good luck