The 172 Driver is correct about GPS being the navigation system of the future but following the line on a GPS of any type is not going to help you get the CPL navigation flight test done.
The cheap end of the GPS market will not help you understand the IFR systems that you will encounter in IR trainning and if as your handle indicates you want to move onto the french all electric jet buy a 20 year old computor, that might have something in common with the dreadfull Airbus FMC.