For a good bass performance, try out the Infinity Basslink SM that is sold at xciteaudio.com. I've installed it and IMHO, it has a pretty good bass response and has a rich bass feel to it. But it has it's limitations and many say these underseat subs are just good for SQ. Personally, I think if you just want a nice, rich and compact bass that does not take the breath out of you, underseat is good enough. If you want loud and pounding bass to crush your lungs, then go for those subs that fit into your boot. I've fitted the Infinity into my myvi lagi best and it did not disappoint me in terms of boosting the low frequencies and giving a good sounding bass. I have it hooked to the OEM myvi betamek HU which sucks a lot of a$$ big big time and yet the underseat functions with no noticeable issue for now.