I have a Shimano Nexus 8-speed hub, I think that's the same as an Alfine, right? I like it. Once you get an internally geared hub, it's hard to go back to derailleurs.
If you're using a normal size (26", 700c or 27") wheel, you typically want a 2:1 ratio between the (front) chain ring and the (rear) cog, i.e. 38:19 or the like. If you use smaller wheels, increase the ratio; for 16" wheels, for example, 52:16 works pretty well. Work out the details with a
gear calculator.
I also have dynamo hubs on the bikes I use much. I like them.
If you are looking at putting new hubs in your wheels, I strongly recommend learning to build the wheels yourself. It is not rocket science; in fact it is a lot of fun, and if you follow the excellent instructions found
online, not much can go wrong.