A subwoofer should be more for LFE (low freq effects) which are "non directional" meaning you can't tell where the sound is coming from, instead of in stereo...it is possible you have your crossover setting to high on your receiver and are picking up the higher freqs. Also, sub performance can change just by moving a sub a few inches. A corner position usually gives you the most output, however, may be boomy or not give you the best overall flat response.
Two subs placed in strategic locations in a room can give you a better balance, but with smaller rooms it may not be needed. Proper position of the sub and/or left/right speakers make a big difference. Also, you may want to look into bass traps and/or mid/high reflection treatments.
You might want to check the audition thread, there are a few people in Quebec, they may be close to you and let you listen to Axioms.
