I am not going to take the time to compare the two speakers you mention, but an speaker which does 40Hz at -6dB does not play low bass, imo. YMMV
Even if it were rated at 40Hz +/-3dB it still wouldn't play deep bass. It's a 12" woofer in a 15x25x12 cabinet - puny. That equals not great bass. :( I'm afraid you got yourself a speaker that you didn't realize can't do much low end. No amp, cables, source, etc. will correct it holistically. It's simply unable to do deeper bass. If you are seeking much deeper bass you will be wasting your money to pursue other fixes for this speaker.