I like this head a lot, but I would like to get more string clarity. I have messed with the EQ and it helps, but overall the head is extremely thick and bassy sounding. Not that I am complaining... I am looking for a clearer, maybe smoother bass tone overall. I like the 6550 power tubes, I am looking at the pre-amp/driver tubes. What would be a good choice to make this amp come alive?