In short, XLR isn't necessarily better. However, the ATI 2007 is a balanced amp, and the Marantz 7704 will output a balanced signal, so in this instance, I'd be inclined to try a balanced cable.
Not to complicate matters, but you'll want to verify the pin arrangement on the ATI 2007. According to page 43 of the
Marantz 7704 manual...
A GND (Ground)
B HOT (+)
C COLD (–)
The PIN arrangement in this device uses the European method. In the USA method, B is COLD, and C is HOT.When connecting a device that utilizes the USA type of PIN arrangement, replace the B and C plugs on one side of the balanced cable.
If the ATI 2007 is arranged with B as COLD, and C as HOT, you can always just refers (+) and (-) speaker connections to preserve polarity.