If you don't already own them, then don't waste your money on them. As Steve and others are saying, the cost savings are close to nil over the smart strings and the dumb string controllers cost more money than the SSC. Also, if you use a controller like the MR16 or the one at the top of the thread, now you need DMX and Pixelnet. Going with just smart strings eliminated the need for DMX, at least as far as the nodes go. Also, with one of these controllers you will need additional power supplies, cabinets, and wiring.
I know that some feel that dumb strings are a good starting point but in reality, you can configure the SSC in string mode and your smart string acts like a dumb string with 3 channels controlling the entire string. Later, when you decide that you want to advance your show, simply reconfigure the controller to either hybrid or pixel mode and you have full pixel control without costing a penny more and no changes required to existing layout unless you decide to move something.