Any effects that modify Amplifire’s power and/or toughness without setting them to a specific number or value will apply after its base power and toughness are set, regardless of the order in which those effects were created. The same is true of counters that modify its power and toughness.

If you reveal your entire library and don’t reveal a creature card, Amplifire becomes a 0/0 creature and you put your library back in a random order.

Amplifire will be a 1/1 creature from the time your untap step begins until the time its triggered ability resolves during your upkeep.