Is it possible to hook up my TM501 to the opposite end of the house and use that to send the DS10A's signal to the CM15A on the other-side of the house?
I am guessing you mean your TM751. One thing to note about the TM751 which is talked about in the forum quite often is the fact that the TM751 is not polite when it comes to PLC transmissions. This means that it has no regard for other transmissions that may be on the power line and may walk all over them. You can try placing the TM751 at a point furthest away from your CM15A, but any DS10As that are mid way between the CM15A and the TM751 may give you some trouble.
I don't know how comfortable you are with a soldering iron to perform a mod on your CM15A, but there are different antenna mods out there that will increase your range on the CM15A. One of them involves exchanging the antenna with one from , ironically, a TM751
shown here. Another mod involves removing the antenna and adding a coax f-connector and making an external antenna.
This link has the instructions for adding the coax connector, but it is an old link and the pics are missing.
This is a link where someone recovered the pics for the F-connector mod.. Then the last step is
making an antenna. I myself have found that the F-connector mod with the antenna is the best. You can mount the antenna almost anywhere. Many have mounted them in their attics. I simply put mine close to the center of the house in the basement. It covers all of my house and about 70 to 80 feet into my back yard.
Performing one of the mods should improve your range to where you wouldn't need the TM751 at all.