A linear supply may give better performance (also more heat) than a switcher. The supply you linked to is bipolar (the circuit diagram in the assembly instructions shows this clearly, with a positive and a negative voltage regulator), so it can produce +12, 0V, -12 (or +15, 0V, -15). There is no figure quoted for ripple, so they make no promises there.
However, look at the power rating (remembering that power is voltage times current, so the 750mA rating will be for the ±5V option):
Adjustable positive / negative supplies: ±5 to ±15VDC, 175mA to 750mA per supply
and compare with what your power amp needs:
Supply voltage: 12 to 18V DC / 1 to 2A
The power supply is likely fine for the preamp/ balanced input section, but is very underpowered for the power amp.
Then again you already have a unipolar power supply which works with the power amp, right?