@JoeMcJoe:
Is it possible to use a 2 port pfsense box, and then use VLANs with a managed switch to connect to multiple DSL modems, all using MLPPP on the pfsense?
I know an unmanaged switch won't work.
Being in the hardware forum I'll give you the hardware portion of the answer: yes. To pfSense, as far as it pertains to software functions, VLANs are no different than physical ports.
Now, the other half, getting multiple DSL modems to load balance, that's a question for the Routing and Multi WAN section of the forums: http://forum.pfsense.org/index.php/board,21.0.html You might get better answers from there since more of the guys that know quite possibly hang out there more than here.