I told the man it was too high on the first or second page. If the output is not enough then you either need to get a second amp and strap them, get a bigger amp, or get another sub and amp combo. You are going to end up wrecking your amp or sub or both. If you don't want to listen that's fine, but quit asking if its okay because we have told you it's not.
If you are waiting for someone to tell you it's okay so you feel better about doing it then fine, it's alright. It might sound even better if you turned the gain up to 7 or 8.
Also, the gain is not a volume control.