I agree that swapping out the PSU with another INTERNAL replacement would make sense, but having something external seems silly to me.
But I've also commented on this subject in the past, with regard to the SE/30:
http://68kmla.org/forums/viewtopic.php?p=2472#2472
Specifically, I discussed with Tom Lee about the need for separate, isolated +12v lines off the replacement PSU in order to drive the Sweep and hard drive without generating noise on the CRT. On a Plus or earlier, you wouldn't have to worry about an internal HD as they don't support such, but if you were to use +12 for something other than Sweep, I would expect the situation would still apply to you; namely, that you would need two isolated +12v outputs from whatever PSU you choose. That's not to say it "wouldn't work" with only a single +12v. But two isolated outputs would eliminate noise on the CRT.
But I've also commented on this subject in the past, with regard to the SE/30:
http://68kmla.org/forums/viewtopic.php?p=2472#2472
Specifically, I discussed with Tom Lee about the need for separate, isolated +12v lines off the replacement PSU in order to drive the Sweep and hard drive without generating noise on the CRT. On a Plus or earlier, you wouldn't have to worry about an internal HD as they don't support such, but if you were to use +12 for something other than Sweep, I would expect the situation would still apply to you; namely, that you would need two isolated +12v outputs from whatever PSU you choose. That's not to say it "wouldn't work" with only a single +12v. But two isolated outputs would eliminate noise on the CRT.