Right around 700 is the sweet spot for the street, off road you may need twice that. I ride crappy streets myself, I use a 400 lumen Phillips Saferide (equal to 1000 lumens due to aimed optics) on the bar, and a Cygolite Mightycross 450 (lumens) on the helmet...however both of these are only used in the low setting on the Phillips and the middle setting on the Cygolite on dark country roads or bike paths or flash mode when in traffic. So 700 lumens of light you will rarely use on high power except for foul weather or dark roads and paths.
One of the best deals around for a light is the Cygolite ExpiliOn 700 for around $104 or the ExpiliOn 800 for around $118. Both of those lights have a self contained rechargeable battery, no separate battery pack to fool with and the battery is user replaceable meaning you could buy a second bat and use it as backup.
The other light which I like better due to appears brighter than the ExpiliOn because of it's aimed optics is the Phillips Saferide, it too has self contained rechargeable batteries that are user replaceable, but these batteries are 4 AA bats which means instead of paying more for a proprietary battery you can go down and buy any brand of rechargeable AA bats you want as long as their at least as many amp hours as the original batteries and of the same chemical makeup. The only con with this light is that it has no flash mode. The Phillips cost around $102; both of these lights prices are on Amazon.
Some will push the MagicShine which I don't really care for. My Phillips light completely overwhelmed a 1200 lumen MagicShine my friend once had before it broke about 1 year and 2 or 3 months. If you want a cheap generic Chinese light like the MagicShine you would be better of financially with this:
http://www.ebay.com/itm/2300-Lumens-...item2a20d71485 The cost of this light with the battery is half the cost of a MagicShine replacement battery! Keep in mind though Chinese generic light manufactures over estimate their lumens by about 100% meaning a 2300 lumen is closer to 1150 which still is not shabby, but keep that in mind when looking at generic brands lumen ratings.
There will be other ideas, none is really right just opinions, you have to weigh out what you want.
Here is some light comparisons to help you see the differences between models and price:
http://reviews.mtbr.com/2012-bike-li...pattern-photos Notice on this one the Phillips Saferide vs the MagicShine J808 on page 2, what a joke.
http://reviews.mtbr.com/2013-bike-li...rd-beam-photos
http://www.performancebike.com/bikes...ghtBuyersGuide From some of the lights that Performance Bike sells.
http://www.thebicyclerepairshop.com/...ison-test.html This one on the top half of the page has 4 of the best tail lights on the market, I own the Light & Motion Vis 180 (not the Vis 180 Micro) and that light looks like a safety flair in broad daylight! it's that bright. I also have the Planet Bike Super Flash Turbo and pales in comparison to the Vis 180. A quick note on tail lights, European studies have shown that a steady tail light is safer due to motorists found it easier to judge distance...but Canadian studies have shown flashing is better due to motorists saw it quicker, so what to do? I'm not sure which is safer but I took the route of both, my main light the Vis 180 I leave on steady, the Super Flash, Soma Road Flares, and the Cateye LED600 are all on flash mode at night. So I cover both spectrums of thought, I have no proof my way or one of the other ways is better, it's just what I do because of what I've read. In the city like I mentioned I again cover both spectrums, helmet light flashes bar light steady. Flash mode does save batteries but with rechargeables who cares?