Multiple ATM virtual circuits, to multiple ISP's, is not supported by any DSL ISP in the US that I know about. It's a common feature of any DSL modem bridge on the market that allows customer access to the internal settings. However, the typical US DSL provider only allows one VPI/VCI pair to the DSLAM and Redback router. There's no reason to do this except that it keeps competative ISP's from easily providing backup and fallback services.
I have not seen any conglomerated DSL/router/wireless/printer/etc box that can do multiple ATM virtual circuits. It would be difficult to impliment because each connection would have it's own IP address. You would need a rather exotic router, possibly with "channel bonding" technology, in order to do anything useful. There are routers that will handle multiple multiple broadband connections. These will balance the LAN side network load between either of the two broadband connections, but will not aggregate the broadband bandwidth into one connection.
Perhaps it would be helpful if you would disclose what you are trying to accomplish and what you have to work with? Perhaps a description of your "massive problems" might be helpful.