Your post omits a lot of relevant information. The Yamaha Sub output frequency and slope is not specified in their spec sheet or in the manual, although some online say it is 100Hz, others say 90Hz. [In the past (before digital bass management) Yamaha always had the sub out at 140Hz, 12dB/Oct]. You neglect to identify your subwoofer, except to say it has speaker wire in and out. Some subs put an electrolytic cap in series with the speaker output affording 6dB/Oct. High Pass attenuation to the attached speakers, others don't (and whether an audiophile wants a cheap electrolytic in series is also a question). You also don't say what your speakers are, and whether your system's subwoofer implementation up to now has been satisfactory to your taste. Your new amp has no preamp in/out connections, so a real crossover cannot be used. My advice is probably to continue using it as you have been, but filling in the missing details might make me revise that opinion.
Subwoofer Out VS Subwoofer Crossover
I have been running a sub for many years now. I string the speaker cables to the sub and then out of the sub to the speakers. The sub maintains a crossover dial/adjuster. I’m now buying a new integrated amp (Yamaha 701). It has a dedicated rca sub out channel. If I use the sub out, I won’t have a crossover control. Should a still string the speaker outs to the sub and ignore the sub out if I want crossover control? Is one better than the other. I like my crossover control.
Thank you.
W