I just picked up a pair of RF-7's (series 1). Couldn't resist for the price ($200 including a pair of MIT AVT S3 cables)). They are being driven by a Pioneer Elite SC-71. The rest of the system consists of an RC-25, a pair of RB-61's and a 10" sub. Just curious if a better sub would be a "nice to have", or a "need to have". The sub I'm currently running is the Mirage Nano sub (again couldn't resist the price of $0.00). I understand this question is open for opinion based answers, but I'd just like to hear some input.