With two separate WAN connections, the best that can be done is policy routing with failover.
You designate your main WAN connection, to which outbound traffic is sent by default. If this connection is down, traffic is sent to the other WAN connection - that's the failover bit. In addition, you can set a series of policies, which are rules that direct certain traffic to particular connections. For example, you could have a policy directing traffic on a certain TCP port used by a game to the ADSL connection for lower latency.
You could use both connections as tunnels to some sort of aggregation service, but you will not be able to take advantage of the different qualities of the two connections that way.