You can get adaptors that allow you to use your factory controls on SOME aftermarket h/u's. AFAIK there's a mob called Eurotech in SA (
www.cartoys.com.au) that have them for some Alpine and JVC units. Dunno about other brands though

. I emailed 'em ages ago and the adaptors were $49. You can either order their catalogue ($10 postage) or just email them like I did.
As far as 5x7's, I'll also add that Kicker and Coustic make them. Also JL have 2 sets of 5x7, the TR570-CX (coax), which are ok for the $$. And the XR570-CX (splits), which are supposed to be awesome, but I couldn't find a shop which had them
Anyways, yes you will should notice a big difference when you go for after market gear. Just take a look at the magnets/cones on the factory speakers and compare them to some of the after market stuff. Chalk and cheese imho. btw I don't mean to offend ppl with the factory spkrs, they are very good (esp. for the price!!!), but when you crank it up you hear the difference imho.
Anyways, enough of my rambling
