Where to go for connectivity in VA / DC

Hi, We've recently opened a POP in northern Virginia. The DC does not have a lot of connectivity options to choose from. So we've ordered dark fiber to Equinix Ashburn DC2, we will light it up with our own DWDM, and pick up connectivity there. We do however need a second point to pick up connectivity for redundancy purposes. (that runway from IAD is pretty scary) Initially we had thought to pick up that connectivity at Coresite K-street. However many of the carriers we use are not available at K-street. What would you guys advise us to go to for lots of connectivity options. Thanks, Bas