How much light is enough for year round commuting?
Going fast on unlit roads you definitely want a decent light. Personally I find the combination of my 100 lumen dyno headlight plus another 100 lumens on the handlebars to be enough, but I ride relatively slowly and on a manoeuvrable bike. On a faster bike with handling and brakes designed for speed you want more. Perhaps not 2000 lumens - that's off road singletrack territory. And price. If you get a better quality 200-300 lumen light that actually puts out 200 lumens you'll be much better off than with an off-brand "500 lumens" that is actually 200...

One consideration is how people coming towards you. While it's annoying to hit a small, dark-coloured lump and end up on the road, it's worse to blind an oncoming motorist and end up as a hood ornament. It's not as bad on bike paths, you're more likely just to get beaten up if you blind someone. Paying a little attention to how much light, and where you're pointing it, is important. With a high powered helmet light it's really important not to look at people's faces... when normally you should be looking there. My preference is to have a relatively low-powered helmet light for that reason - I can still look at faces, and people will see me but not be blinded unless they're already very close.

Nathan's Bike Light Database is a good place to start.