I had the Juno Stage for 2 years and the Fantom XR for a short time. The WaveROM of both instruments has the same size of 128 MB, and a lot of the sounds/samples are identical. The Stage has a few newer sounds, mainly I think in the acoustic guitar area (stereo samples), and as these have a larger WaveROM, a few other samples in the Stage had to be downsized, e.g. the Ultimate Piano, which has fewer velocity layers. I'm not sure about your preferred sounds in the synth area, that's not my main interest. But I'm very sure that the SRX 07 has lots of good patches/samples which are definitely NOT included in the Fantom X ROM, so you will definitely have a better choice of sounds with a Juno Stage + SRX 07 compared to a Fantom X without SRX.