Seitronic LED angel eye upgrade
 

I had a stock bulb fail and discovered the replacement price was about the same as LEDs. I poked around a bit on Amazon.de and read the German guys' reviews. Germans are quite brutal and frank if they don't like a product. I settled for Seitronic brand (see pic) which had the best rank and comments in its price range ($55).

So far, excellent! (see pic) For the price of stock replacements, it's a no brainer as we say in California. Here's the link to Amazon.de. Seitronic LD-560 LED Angel Eyes Xenon Weiss: Amazon.de: Auto Hopefully you can find Seitronic in the US too.

They are not as bright as the DRLs on my E70 when it's on daylight setting. But my E53 has no day setting, and the night setting is about the same brightness as my E70. I realize that my E53 only has two wires to the bulbs, so unless BMW varies the voltage to the bulbs on that pair of wires, only one brightness is possible. Perhaps someone here has crossed that bridge?
http://i67.tinypic.com/2mi0rid.jpg
Not sure where that weird reflection came from in the middle between the two X5s...

http://i65.tinypic.com/2u6ibn8.jpg

You are limited to the brightness due to the optics of the actual rings in the headlights. For the price and labor, the bulb replacement is the best you can do on the E53 facelift.