The safetest, easiest and most cost effective for upgrade from standard 55/60 H4 bulbs is Philips Vision Plus which is the same wattages. The cost for a pair is $28, shipping included, from:
http://www.autolamps-online.com/home.htm
I had VP H4 on my Lexus LS400 about year and a half ago, and I can say that they are much brighter and whitter than the standard bulbs.
Relays and beefing up wiring are to reduce power lost from battery/alternator to headlight bulbs.