Yes, try to get PPPoE working, your performance will improve greatly under a heavy load. Often times the routing tables on modems can't hold all that much, they tend to all but crash after a couple thousand states hit it. My ISP says they offer PPPoA only. Here is how you see if you can run PPPoE anyways. Set your modem to transparent bridge, that makes it just a media converter basically. Then just set your wan on pfsense to send your PPPoA user/pass. My experience has been that it works just fine, althought I haven't tested it with that many ISPs.