I have the stock 8 spd cassette on my Tikit and after wearing out the first one I just got another. It gives me a low enough gear to get up the climbs and by the time I spin out I'm going as fast as I want to on that bike. My NWT uses a Nexus 8 IGH and I find that fine as well. I coast on really steep hills so I don't need a big gear for that. My limit is how fast I can spin vs. how fast I want to ride on the flats.

I guess the question is how fast do you want to ride on the flats and how fast can you spin?