I agree with Tim, although I'm new to the forum, I've been running infinity's in my maz, nothing but good sound. As for alpine, I can neither boast nor bash them. But I'd say you can't go wrong with the infinity speakers.
Although the saying you get what you pay for isn't always true, in terms of comparing the reference to the kappa series speakers, I feel that you are best dishing out the extra dollars for this upgrade. My best advice for you is that after you have selected the models you like, take a look on www.pricegrabber.com or www.nextag.com. Put the Part numbers in there and take a look. You can usually get the speakers at a relatively low price. Furthermore, I find the www.gopcplus.com despite the fact that they deal in computer parts, they can usually get you some insanely low prices on all new infinity speakers, which also carry their warranty. Take a look.
I'd stick to Kappa or Kappa Perfect lines. I have two sets of Reference and while they are ok, the power handling is fairly weak, and they are very bright. The Kappa lines are much much better component sets.
Yeah, go with the Perfect's if you can, otherwise the kappa's are still pretty much better than anything else you could get. However, im not sure but i think the Kappa Perfect line is only for subs, and maybe component systems. But in regards between reference and Kappa. go with the kappa's all the way. You'll get more than what you paid for.
Also check out ebay. But stick to the ebay stores, i don't trust private sellers.