Everything Jugglering, fo3nix, and Chuck said.
I have a system - old now - of separates, e.g. an Arcam amp, Philips CD drive, Wharefedale speakers, high quality cable, no more than 40w per channel, but I barely dare take it above half volume. The speakers are on stands, and on the ground floor with underfloor space to enhance the bass and resonance. It is a very old system, but I have heard nothing modern to surpass it without going to silly prices. For a bit of balance in your hunt, try visiting the websites of a few top-end British manafacturers, such as Linn (Glasgow) and Ruark (Southend-on Sea). The prices will amaze you ! For the very rich and fortunate.
You will find it hard to achieve the same sound quality if you are in an upstairs flat, because you are on a solid floor with no under-floorboard cavity. When I lived in a flat, my system sounded very different (nowhere near as good) from now.
What I would suggest is finding a store that stocks older equipment from the 'golden' age of hi-fi separates. There is one in Croydon, where you can pick up very high quality second-hand separates for around �100 and they will out-perform today's juke-boxes and add a bit of design panache to your room.
Happy listening !