This light is rated around 280 to 300 "Chinese Lumens", i.e. it's probably in the 200 - 250 lumen range in reality, but that's still pretty bright. It uses 14500 LiPo batteries, which are very close in size to AA cells but are a higher voltage. You can use AA cells but the flashlights will give something more like 100 lumens each if you do.
These are Q5 crees, so be careful that you don't get a dimmer version such as a Q3 because they're sold in identical enclosures. Also these are frequently sold at a discount so Google for coupons or check on sites such as Slickdeals for a good price.
Unfortunately because of the batteries and accompanying charger, the cost of the components is more than the cost of the four flashlights (ie under $30), but if you already have some of those cells and a charger (or just want to get some anyway to try stuff out) then this is a cheap build, otherwise if all you want is a very bright light off the shelf, look around for a good price for a Magicshine of equivalent output, it'll take up less space on your handlebar and won't cost that much extra - maybe $60 total.
This bundle will get hot if you turn on all 4 lights for an extended time and are not actually cycling, which is needed to keep the temperature down due to air flow. However it does have the advantage that you can get an extended run time by simply not turning on all four at once!