One question to ask yourself I would suggest is if you have any plans or expectations to upgrade the rest of your system? The issue with changing one component - an amp, say, is that while it might bring you an improvement, it might equally unbalance your system, highlighting other deficiencies elsewhere that previously went unnoticed. Then you end up changing your speakers, your TT, your cabling, until you end up finding that balance again, albeit at a higher price / performance point.
That said, looking at your kit list, it's not budget stuff. You have some lovely sources and speakers so you may find an improvement, or at least a different "flavour" with a change of amp. Nothing wrong with scratching an itch, just be aware that you might end up scratching more than you thought!
Moving to a pre / power (or pre / monos) combo is often the way people go but there are equally some mega-integrateds out there - Luxman for example, that will show a clean pair of heels to a modest pre / power setup.