Having multiple sites to segregate AV updates?

I'm exploring ways to segregate my servers into update groups in order to not have all 800 downloading antivirus updates close together in time.  Our heartbeat interval is 5 minutes (can't change that) and when the servers start to pull down the new defs, our SAN slows to a crawl.

I'd like to either create a new site (or two) and split up the servers into smaller update groups, or else come up with another plan for rolling out the updates - maybe there's just something that I'm not aware of that would work?

Anyway, if I wanted, could I create a couple of new local sites and if so, how would I do that?

Thanks,

Mark