Dan, I think part of the problem with lack of bass in the '00+ cars is that there is no enclosure around the speaker. This makes ALL the difference in the world in speaker sound. It was a poor move by the designers, but I would say I would not worry too much about bass up front -- anything below ~80Hz is very hard to detect the location of using our ears, therefore that is the reason why you can get away with putting a sub in the trunk.
I agree its silly, but it is what it is....plus those expensive Infinities you have are not designed for gut wrenching bass anyways, it'* a 6.5/7 inch speaker
'02 Aurora 3.5, factory NAV retrofit, CD changer retrofit, Philips Xenon lights. '96 SE: Gone but not forgotten :( Oh yeah, and a few other toys.