That sounds like a plan. But I would offer that rather than mess around with a splitter and then as such any potential conflicts which there may be, just go ahead and and put the money towards a dual lnb (if it's not already) so each receiver can have a dedicated source.
You say you now have a DTC-100. Have you disconnected your Dish receiver and hooked up the DTC-100 to the line yet to check signal strength or anything?
You say you now have a DTC-100. Have you disconnected your Dish receiver and hooked up the DTC-100 to the line yet to check signal strength or anything?