Office 2004 is fine under Snow Leopard. In fact, so is the older Office X from 2002.

The interesting thing about Apple's advertising for Snow Leopard is that, while they say you need the $169 bundle if you're upgrading from Tiger, the $29 box that they say is for Macs running Leopard is actually clearly marked "RETAIL" not "UPGRADE", and it will install just fine on Intel Macs currently running Tiger, or even Intel Macs with new or erased hard drives. And the licensing agreement, which you have to accept to proceed with the installation, makes it clear that anything labeled "retail" doesn't have to meet any requirements for current OS versions.