Hey folks, I have an old Logitech z103 2.1ch system that sounds pretty good in moderate volumes but the BASS is not smooth rather it sounds shaky at more volume. The sub is an 2 amp 4" driver unit. I suspect the sub is not powerful and if so, would like to replace the sub (Only sub driver not the enclosure)with a more capable one. What to look when doing this and may I do this or not?, I appreciate any help. Thanks in advance.