I am thinking about upgrading my speakers to infinity references in my alero. how big of a difference will this make is it worth the money? also how important is an amp for the speakers?
Coaxials or Components? If you get the coaxials, you'll be fine running them off the HU. If you get the comps, you'll need a small 2 channel amp to power them effectively. Either way, Infinity is a good upgrade to stock speakers.