Honestly, I know NOTHING about the MX-3 so I cannot comment on whether or not it is good or bad.
However, the Lynx 3D is an Excellent choice! The ONLY complaint I have ever had about it was the documentation. However, once you get beyond that, everything is a plus!
I also only run the spectra module with the Novak XXTra FM Synth RX's. The RX's can get a little pricey at 90$ a piece, especially if you have a handful of cars. The other option would be to relocate the RX from vehicle to vehicle if cost is an issue.
-Chris