@ti33er I think you are referring to the law of diminishing returns.
You could spend £1000 and get a sound that is perfectly adequate, or spend £2000 and get a sound that is 10% better (for example) and so on, so on. It all depends on what is important to you and where you want to draw the line and compromise / settle.
My line was drawn at an Arcam AVR550, an external DAC for music, a 2 channel power amp for my atmos speakers, and a mono amp on my centre. This combination brings me a lot of pleasure, and hits the spot where a lot of other (as it happens, lower cost) AVR's and amplifiers failed to really impress me.
I am probably not going to explore the new range of Arcam's because I have a set-up that I am really enjoying, and I don't have the budget to keep reaching for another small percentage improvement.