However, I get some great tones with a generic NOS 5965 and a
SOVTEK 12AX7EH (or amazingly, a cheap Sovtek 12AX7WA),
the NOS 12AY7 with the supplied 6V6EHs and 12AX7. 
I don't like the 5751 much in any position in the 5E3 and I hate any
12AX7 in the first socket!
The 5751 is still too hot for me installed in the first preamp socket.
Out of a total of over fifty 5E3 amp kits I've put out and helped
guys build, seven of them have been returned to me as being
defective or in operative.