I have not found any difference between connecting at the amps vs speakers with my pair of REL T5x on several different amps except for my Naim. For some reason the volume output was reduced when connected at the amp.
With stereo pairs, REL recommends placing the subs next to and slightly behind the front of the speakers. If you place them like this you can use a shortened cable to the speakers, rather than one that has to go all the way back to the amp.