Thanks everyone. I'll play around with the speaker positioning, and try out some Mission standmounts I've got in another room. At some point decision needs to be made about source (laptop vs streamer) and active vs passive speakers.
Room is 5 x 5 m, 3m ceiling i.e. a box. Not much in the way of soft furnishings but one sound absorbing panel opposite speakers, wood floor covered in carpet. Speakers are 1.2 m in from the sides and about 0.4 m into the room.
My current system is: Macbook Air -> HRT Music Streamer II DAC -> NAIM Nait 5i mk 2 -> Tannoy DC6T
Streaming Spotify and various other web sources.
To my ears the system sounds good but a bit flat. The bass can get muddy but that could be the room rather than the system.
Any suggestions for...