Both the trigg & Becker units are very good and I would be happy to fit either one in a two seat aircraft, the com performance for both is very good and so the decision will come down to ease of instalation in the particular aircraft and the intercom that the units provide.
As you are removing the Narco this unit that uses the Trigg tx unit might be of interest as it will fit the same panel width, I have always found the PS engineering intercoms superb.
http://www.ps-engineering.com/PAR200.shtml
What ever you decide you will be light years ahead of the Narco in terms of quality and reliability.