Hello Sparky
I am sure they are one or two other RSA users on here as well, so their contribution would also come in handy to
We are lucky to have a couple of reference clocks in the lab, one Rb one GPSO.
The OXCO upgrade on the Rigol RSA does make an appreciable difference especially as well the unit 'off site' at customers as well.
Taking a master clock along is not a viable proposition! Yes you do notice a positive difference with the clock upgrade, you may not have to take your RSA out on 'missions' so you may find for the cost outlay just constructing a decent ultra low noise power supply for the GPSO will work absolutely great for you.
The way I have viewed this is simple most of the labs (professional) we deal or have dealt with, all use some form of master/slave reference clocking system, and pretty much all their scopes/SA/VNA's have the OXCO upgrade as well.
I feel personally it makes a difference others may not, however one issue when considering this method quality cabling or the correct length.
Nice to see a fellow RSA owner stepping out of limelight!
I do feel that having the upgrade internal clock is worthwhile, however for the outlay you can built a really top notch GPSO and have enough left for a good time away on a Rugby weekend outing!