I looked at your systems listed and no mention of a Jolida? Hard to give advice on a good upgrade if your system isn't listed.
The 302b and the 502 Jolida are the same amps. The circuit and transformers are the same. It can be changed to use KT-88's or EL-34's by changing four resistors in the bias network. My 502 run's both KT-88's and EL-34's. You may or may not like the KT-88's better. I do because I like the extra power with my Vandersteen's. There is a lot of debate on which tube sounds better. Hope that helps. By the way I wouldn't sell it. I love mine since I did all the mods.