I bought a different model Furman. The 3 amp continuous and 45 amp peak reserve is provided by it’sinternal power storage.
I have a separate 15 amp circuit, but, like OP, not necessary using a Furman (or other similar unit) Essentially you can fill it with dirty power, out comes purified power capable of instantaneous bursts of power without immediately needing/using the dirty power that ’fills’ it. 3 amp continuous is a LOT!.
I turn the whole system on/off with it’s switch, never experience anything that hints at power as the source of a problem.
With everything fed from the Furman, there’s no reason to buy expensive cables for your components beyond that provided by OEM.
Considering capacities, remember, only one source is drawing power at a time.