Ok, I looked at the link you posted about "fastservers". Is this the location where you datacenter is collocated? If so, the listed text shows that the connection is dual OC-48's which each operate at 2.4gbs. This is much higher than your 100Mbs, which would answer my question. Is this a correct assumption?

If this is the case and your gear is collocated, you might have a problem getting a hardware VPN product into the mix. Software might end up being your only route. From the looks of things it looks like you don't own much of the infrastucture? Let us know how your stuff is currently configured.