Gretsch 6120 Jnr upgrade or not

[Billyboygretsch]

I have had one of these for quite a while now. Replaced pick ups with TVJ. Have been thinking for a while now of putting in a middle pick up just to give a bit more variety. Looked at the 5622t but does not sound very Gretschy probably because of pick ups and centre block. Guess will cost around £200 to do it. Will it lessen the value of the guitar or should I keep it as is