Do you not have a separate amp channel available as it would be better to use inline RCA type filters than these you show which will be more lossy.

For instance, I have the two rear speakers on one channel of my 770, but they are 8 ohms and since the back channel is really combined in most cases, using the same channel works.

I have used both these:
http://www.partsexpress.com/webpage.cfm?...=195&manuid=265
and the filters you pointed out and both work fine.

It also appears that your trying to use the Marantz to power the sub and rear channels and you might want to consider using the Marantz to power the rear channels and get a plate amp for your sub since you can get a good one for $100-$200 just to power the sub.