Ted, have you heard about the ekat-site? It has exploded views of all festool tools, with part numbers and prices. If it would really be that usefull to you, you can just order the base seperately, and you can then quickly change one for the other, without screwing the tabs back on or off. (I haven't checked the price yet of the replacement base, I'll check and post a link)
The ekat-site can sometimes be very usefull, because some tools are very similar and by changing a few parts you can convert them.
Best example I read was from Riri at the Aussie forum. He had a project where he needed to strip and bring up the grain of old floring, and festool makes a tool that's perfect for the job, but because it's a bit for specialty use, rental companies don't have it, and it was priced rather steep for a one off job. We then noticed the similarities with the festool renovation sander (the 180 mm version of the RAS115), so he ordered the special tool and the parts to convert it to the renovation sander, a tool wich would see more use in his regular activities. (He did so after confirmation from his festool dealer it could be done).
/edit:
here is a link to the US ekat-site, you can find the domino under the routers section (I can't link directly to a tool, just to the overview). There are two versions of the drawing for the domino, the top one is the one with the tabs (...120V). The base consist of a lot of parts and won't be cheap, but it would be less pricey than a second domino.