I've used a variety of hub gears over the years for commuting and hacking around.
The SRAM and SA 3 speeds are reliable and efficient but I doubt they'll give you enough gears or the range you need.
I ran a Nexus 7 for may years. It was reliable and needed no maintenance. Gear range wasn't that big (about 200% IIRC). Used it with a roller brake which, with the gear cable cassette, made wheel removal difficult. Stopped using it after the rear wheel was written off in an accident.
Used a SRAM Spectro 7 for many years too. The bike has very short rear stays so the the clickbox intefered with my heel sometimes. Otherwise this would be my favourite. Extremely reliable. Good range (around 275%) of gears and pretty efficient in the middle ones that you use the most. Wheel removal with the clickbox is easy. The rim's just worn out so I've put myself a Premium (roller bearings on the pinions) Nexus 8 (the new SG-8R36 with the better seal) in a new wheel.
Haven't used the Nexus yet but it looks like it should be reasonably efficient across the whole range. Gear range slightly higher than the Spectro. The earlier models had a bad reputation for reliability because the seal was bad, I believe, and let water into the internals. It needs maintenance - remove the internals and dunk them in oil. I don't believe this is complicated (if you're reasonably competent) but you would need to but the Shimano oil and something to use as an oil bath. This is every couple of years or couple of thousand miles. My Nexus 7 needed this in theory but I never got round to it in it's 3-4 year life of daily commuting.
The Rohloff is very expensive. The i-Motion 9 quite expensive and possibly not proven as reliable as the original SRAM hubs yet.
The i-M 9 and the Alfine will take a disc brake. I believe you can get an adaptor to put a disc on the roller brake splines on a Nexus hub. SRAM 7's are readily available with no coaster brake but fitting a disc isn't possible.
In the UK Madison import (most) things Shimano. Fisher's import SRAM stuff. Roman Road Cycles and SJS do a lot of hub gear stuff too. Germany is a good place to source stuff - check out
www.roseversand.de. Google around - I haven't got all the bookmarks on my company notebook.
I would guess that given your description of the intended use 7,8 or 9 gears would suffice. You can bias the range the way you want by changing the sprocket size - choose more lower gears at the expense of more higher gears or vice versa. A 36 spoke large flange hub gear in a 26" rim will give you a bomb proof wheel and a 700C will be strong too.
You will only get flat bar controls for & speed plus hubs. I believe SJS sell an extension that fits in the headset stack to fit one if you have drop bars. The other approach I've seen is to clamp a smaller diameter tube inside the end of a drop bar.
My recommendation would be a SRAM 7 - but only you know which factors are the most important.
edited for typos!
