EL34's on ASL Hurricanes??

Definetly get NOS 6sn7's. It makes a big difference. I swapped mine out for Sylvania's.

First you could see about changing out the input stage tubes as this will be a lot cheaper and might get you the desired results.

Borrow a tube preamp (Conrad Johnson (older one for the sound your looking for) Audible Illusions L1, etc) first.

If you have silver interconnects or speaker cable pull that out and try something else.

Try vibrapods underneath your CDP or some other sorbothane isolation or remove points if you are using them.

I used both EL34's and 6550 in my Music Reference RM9 and I can say I really appreciated the bass control and the treble extension that 6550's afforded my system. Also I switched to an Audible Illusions L1 preamp from a solid state preamp.