Caps typically work best when run up close to their nominal rated capacity. Having said that, these caps will work fine and probably better than what you had in there before.
One suggestion that i would make is to "form" the caps prior to installation. That is, find someone that can bring the caps up to or very near rated voltage for an extended period of time and then let them sit for a day or two. Discharge the caps in a safe manner than then install them into the circuit. Keep the leads as short as possible and use a heatsink ( alligator clip ) attached to the lead when soldering. Applying a small amount of "blu-tak" or something similar around the point where the lead enters into the body of the cap can also help reduce capacitor induced microphonic distortions.
All of this might be beyond the potential capacity of the Marantz speakers that you're working with though, so use and apply as you see fit. Either way, what you're doing should improve the performance of the speakers, but be prepared. They WILL sound markedly different, especially at first. I wouldn't expect them to sound "good" until you can get quite a few hours on them at pretty reasonable volume. After that point, the sound should clean up and be more focused, losing a lot of the bright edge that you'll initially hear. Most of the time, fresh solder connections & new caps in a speaker sound absolutely horrible to me, so don't be dismayed if you run into a similar situation. Sean
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PS... while you're in there, check out what they are using for internal speaker wire. I'll bet that you could make some forward leaps in that area too....
