I have a Tivo HD with a Tivo wireless G adapter and until recently used a Linksys WRT54GS. Netflix via the Tivo streamed flawlessly for the three years I ran this configuration, never once overrunning the buffer while playing. I recently replaced the Linksys with an Engenius 9850 but kept the Tivo G adapter since I had no reason to upgrade that component.
Tivo's are easy to feed (meaning the bandwidth required is not excessive). As you noted TiVo offers G and single band N wireless adapters, so if you're shopping for a new router just to hook up the Tivo dual band N would have no obvious advantage over single band N. And, based on my experience, an existing G router may be sufficient.
FWIW, I'm pretty happy with the Engenius. Seems like a good value.