what specific model number?
you can always get a sub that has both speaker wire in/out AND rca in/out.
rca in/out is best, it takes the load of low frequencies away from the main amp and those frequencies away from the front left and right speakers; both the amp and speakers get a break, lets you use a less powerful amp, perhaps then use tubes. sub sends everything except low bass back to the amp, via main-in.
speaker wires to/from sub does NOT give the amp a break. main amp still amplifies all the frequencies, including the bass. the sub takes the bass only, send everything else along to the front left and right speakers, so they get a break, don’t try to make low bass, thus stay cleaner doing everything else.