NAD C316BEE V2/Subwoofer dilemma…

I thought I had my bases covered, pre-purchase-research-wise, but I’m being told by the mail order outlet where I bought my NAD C316BEE V2/Klipsch RP 600M combo that adding a sub is a no go…”You might be able to wire up something in parallel but the output would never be satisfactory.”  I was looking to add an SVS SB-1000 pro active sub (with speaker level inputs).

Can anyone more knowledgeable than I confirm whether or not this is the case?  At this point I’m not sure if the tech person I’m talking to at the mail order house is the real deal or some high school age Christmastime help…

Thanks in advance.