On the Sturmey 8, with a 25t rear sprocket, and a small front chainring, you'll be OK.

Really, I'd suggest the Sturmey 5 instead. It is more durable, more efficient, lighter, it uses standard sprockets, and the gear range is only slightly smaller than the 8.

The Sram 5 costs more and has the annoying clickbox, so I'd go with Sturmey in the 5 speed.