@trentdk:
I'm just curious as to why the Linksys router was supposedly sending information (a lot, apparently) while purely downloading, whereas the pfSense router, more expectedly, does not 'send' anything while downloading.
If you are downloading over a TCP connection (e.g. ftp, http) there is no such thing as a "pure download". The TCP protocol requires the transmission of ACKs to acknowledge data, hence there will be an apparent "upload" of "control" information as well as the data download. This is true regardless of the router.
I suspect there isn't any precise specification of what the SEND light means, so it could be misleading to read too much into it.