I had those S4s for several years and liked them very much. They sound more like floorstanders than bookshelves. I like them a lot. To me they sounded slightly sweet but very fast, punchy and detailed. I preferred them to my KEF 201/2 which at one point retailed for 6k.
I don't think you are going to get an upgrade for 3k.
I don't think you are going to get an upgrade for 3k.