DEI is def. good bang-for-the-buck stuff, but the problem with using that relay for HIDs is that it requires a trigger pulse, not a constant signal. Meaning you'd have to use a momentary button to manually turn them on - fine if that's what you want, but not automatic as headlights should be.
This one is the best, most compact solution I found - and solid-state transistor vs. mechanical coil (more expensive though):
http://www.wolstentech.com/products/...delayrelay.php