excuse me for jumping in but to understand amps and voltage it may be easier to think of a water pump. Voltage in electricity can be thought of as basically a measurement of pressure differential and amperage as a measurement of flow rate.
In an electrical power supply the amperage rating it has is the amount of "flow" it can maintain before it begins to lose voltage (or overheats depending on design)
So if a power supply is rated at 1amp at 12vdc it can supply that much flow if required without a drop in pressure (voltage) or excessive heat.
If you exceed the amperage rating then the powersupply's voltage will start to drop and/or excessive heat will start to build up.
Of course there is usually a decent "safety factor" built into these units.
If you have a 1amp powersupply but the "load" only uses 0.25a then that is all that will flow, the 1amp rating is a max rating.
personally I would recommend to use a power supply with the correct voltage and at least the amperage that the fan/s are rated, 10% over is always a nice buffer for the unexpected.
Interestingly enough, these fans are axial flow dynamic air pumps and their amperage rating is directly proportional to air flow, so if air flow is restricted their draw actually goes down... I know, counterintuitive but true
so to make a long story short, yes there is room to play... to a degree, but its best if the voltage is spot on and the power supply's amperage rating exceeds the load rating.