Should I choose a WPMU DEV template over the one I've recently purchased?

Hi there,

I'm new to WPMU DEV and almost as new to WordPress and BuddyPress.

I have extremely ambitious plans to build a not-for-profit/nonprofit website for Australian organisations that may grow to 5,000,000+ members.

I want a great template that will work for both WordPress and BuddyPress and am now concerned that if I go with the Templatemonster template I've purchased I might regret it further down the track.

So, as I'm yet to install that template, should I hold off and choose a WPMU DEV template instead?

Thanks.