Get the Core i5. I'm sure it sounds nicer to you guys to have triple channel vs. double channel, but the fact is that the VAST majority of users and applications receive no benefit; in fact in those majority of programs the double channel controller actually performs better. Imagine that.
Also, unless you plan on having high end gpu's in SLI, there is next to no point in considering the i7. The i5 socket will be more upgradable in the future, it will run cooler and use less power, and has turbo boost that will benefit you more than the i7's next to useless turbo boost.
i5, don't let the fact that it's considered "mainstream" or cheaper fool you.