Grohe are indeed bombproof – but with a 3 bar pump ours runs at 15l/min for one head and 25L/min with two heads, and it doesn’t feel excessive. To do that for long enough we need a separate hot water cylinder (210L) and a 22mm direct feed from a water tank – which it can empty if used by all of us in a morning – despite having a completely separate water tank and cylinder for other hot water and cold water feeds…
Such is the lot of a shower addict…
On the other hand my mum has a great little Mira in-shower wall-mounted unit, (event xs?) incorporating pump and valves running with probably a 1.5 m head above it, which does a half decent job from a cold tank and gravity fed hot water cylinder.
Depends what you are really after – but you don’t get near a proper “hotel shower” experience without a pump and a lot of water.