A couple of ideas you may want to try before giving up and buying new speakers.

1) Try setting the mains to "large". (I rarely recommend this, but in this situation it seems at least worth a shot.)

2) Rather than using the fixed 80hz crossover of your receiver, try running the M22ti's through the subwoofer, and using the subs crossover. You can then tweak the crossover as much as you want. You may find a better setting that way.

Good luck!