You ideally want to run the i7 with triple channel memory. Dual channel is perfectly fine and very well performing currently but it's more of an investment thing. If you overclock or get a faster processor you'll probably hit dual channel limits first.
this sums it up for me:
http://www.tweaktown.com/articles/16...it/index7.html
Note the date tho. tl;dr if you have the bucks get some new fast triple channel. Dual channel will work but will probably be your first bottleneck as I understand it.