Hi, there, Scott. Welcome to TalkBass.
Wow! Man! I don't recall seeing or reading about that cool looking Fender Satellite SFX before. But, I see from the
Satellite SFX manual that it is a powered extension cab used "to add the “spatially exciting”
Stereo
Field e
Xpansion effect (patent pending) to your
traditional guitar rig". Hmmm ... ... I bet that gave your Ultimate Chorus and Strat some pretty spectacular sounds!
So, I would think it's very similar to a traditional
guitar amp, who's speaker(s), at least, are not usually designed to handle
bass frequencies at high volume settings. But, also like many guitar amps, it
may give some good bass tones if used
only at low volumes.
Also, it's possible that the
bass frequencies might not benefit from the SFX effect nearly as much as guitar frequencies do. But, I could be wrong.
I'd think, if you could follow the setup procedure in the manual meticulously, that it would be worth giving it a try. But,
alas, the Rumble 40 doesn't have the requisite Preamp Out (FX Send) & Power Amp In (FX Return) jacks needed to connect the Satellite correctly. But
Fender Rumble Club does have, and it's currently going for 25% off in Fender's best ever, but soon-to-end, Labor Day Sale.
[I'm not affiliated with Fender or any music gear vendor.]
At any rate, either you or your son should come tell us about his Rumble 40 in the
Fender Rumble Club and get a free membership!
.