Subs can be connected any of a number of ways. If you have two channels out you can run one to each sub. Regardless of where they are, because sub bass is all mono. L & R both the same. You can split them with a splitter. If one sub or amp has a bypass you can use that to go to another sub. If all else fails or you have no sub or pre-out you can use a line out converter to connect the subs to your speaker outs. There are so many options this is a total non-issue. Unless you want something with a sub out with a filter that allows you to select the rolloff for the mains, something like this https://www.ravenaudio.com/product/nighthawk-mk3-tube-amplifier/
Which by coincidence will make your speakers sing like you never heard before. You will NOT need more power, especially not if you use the sub filter with your subs. https://youtu.be/Gcd76DZmbdY?t=210
Which by coincidence will make your speakers sing like you never heard before. You will NOT need more power, especially not if you use the sub filter with your subs. https://youtu.be/Gcd76DZmbdY?t=210