This has probably been mentioned before, but...
Are the 3 filters, 3 separate filter chips, or are they contained within the same chip somehow? If they are separate then is there a reason why more than one can not be active at one time? It would be great if we could select multiple filters at once so they could work in series (or parallel, depending on the internal structure). I figure it would not be possible as, surely it would have been done already.