The biggest sonic change in my system occurred when I switched from SS to tube. I tried several SS integrateds. I preferred some over others but on the whole, they all had a similar sonic signature.
It wasn't until I demoed an integrated tube amp that I discovered what I had been missing the last few years. Lush, warm, romantic, greater grip on the low end, and a superior sound stage.
I've tube rolled the stock JJ's for a NOS 1960's RCA clear top which was an improvement. But the more research I do, it seems that folks really like the Mullard. So I ordered one and should have it within the week.
You could do something like a used Rogue Cronus Magnum II for about $1,500.
Just my .02, YMMV, IMHO, etc.