You'll want to pickup a set of NGK-BKR7E's from
www.summitracing.com They're $1.99/ea (you should probably pickup 2 sets just in case) and shipping is free although there's a $6 handling charge (for whatever the hell reason).
You're car (e46) uses NGK-BKR6EQUP plugs...one step colder would be the BKR
7E's. They'll be gapped from the factory at 0.035 which is what they should be at (although i'd double check all of em since a couple of mine were off just a little bit). Dont forget to read your plugs often! Here's a nice tutorial on what to look for:
http://www.centuryperformance.com/spark2.htm
hope this helps!