I'd also be concerned about the 100Hz setting on the sub (I think your B&Ws effectively go lower than that no?), and I agree playing with that and speaker/sub placement could help quite a bit. That alone could bring significant improvements if you haven't done so, and it's free. But I don't think it will address the image and tonal density issues you mention.
I doubt upgrading the pre/pro and amp will get you what you're looking for either. It may help improve some things, but for what you're looking for I'd start with the speakers. Either the B&W's character isn't giving you what you're looking for or they just simply can't move enough air to bring the weight of instruments/vocals into the room (I suspect a combination of both). A while back I had the opportunity to directly compare several B&W models (up to the 803s) to some competitors, and it was exactly in the areas of tonal expressiveness and weight in the lower mids that didn't let me feel the expressiveness and dynamic/tonal weight of the music as much -- I think similar to what you're experiencing. I'd highly recommend demoing some other speakers in your home and see if they provide more of what you're looking for, then at least you can be a little more confident in what you do next. Trying other brands, maybe smaller floorstanders if possible, or maybe something larger/further up the B&W line would provide some valuable perspective. Best of luck.
I doubt upgrading the pre/pro and amp will get you what you're looking for either. It may help improve some things, but for what you're looking for I'd start with the speakers. Either the B&W's character isn't giving you what you're looking for or they just simply can't move enough air to bring the weight of instruments/vocals into the room (I suspect a combination of both). A while back I had the opportunity to directly compare several B&W models (up to the 803s) to some competitors, and it was exactly in the areas of tonal expressiveness and weight in the lower mids that didn't let me feel the expressiveness and dynamic/tonal weight of the music as much -- I think similar to what you're experiencing. I'd highly recommend demoing some other speakers in your home and see if they provide more of what you're looking for, then at least you can be a little more confident in what you do next. Trying other brands, maybe smaller floorstanders if possible, or maybe something larger/further up the B&W line would provide some valuable perspective. Best of luck.