Your machine has a 64-bit processor. It will run Snow Leopard no question.
Leopard isn't full 64-bit because it supports 32-bit processors.
Tiger wasn't full 64-bit because it supported 32-bit processors.
Panther wasn't full 64-but because it supported 32-bit processors.
Jaguar wasn't 64-bit at all, even though it runs on the PowerMac G5 (64-bit processor)
G5=64-bit processor
Core Duo=32-but processor
Core 2 Duo 64-bit processor.
Leopard isn't full 64-bit because it supports 32-bit processors.
Tiger wasn't full 64-bit because it supported 32-bit processors.
Panther wasn't full 64-but because it supported 32-bit processors.
Jaguar wasn't 64-bit at all, even though it runs on the PowerMac G5 (64-bit processor)
G5=64-bit processor
Core Duo=32-but processor
Core 2 Duo 64-bit processor.