SBhatia has a very good point, you need to decide for yourself. I have a friend who spent $350 on a pair of focal front component speakers and i dont think they sound any better than my eclipse coaxials. I hate infinity, but i do know people who like the sound of them. You should definately spend the extra money for components in the front but I will tell one thing most people can agree on is that any metal tweeters is not the way to go. Sure they are stiffer and can move a lot faster, but they tend to be really bright and harsh. It is really hard to find speakers with aluminum or titanium tweeters that the rest of the sound isnt overpowered by the tweeters. Try to stay away from the huge name electronics makers like sony, pioneer, or panasonic for speakers. Dont fall for the "wow look at these pioneers, they must be better because they are 4 way speakers." Go to a tweeter if you can find one, they usually have pretty good stuff.
As far as your subwoofers go, i dont really know. As much as i hate rf, some of their stuff is pretty impressive. Like their 6.5" sun in a tube. It is really amazing how much sound these little subs can make now. The sound degredation rate on rf is also much better than other brands. I have had two rf power hx2's, kicker comp vr 8", kicker solobaric l5 8"(not worth it), xtant 12"-loud but kind of poppy, mb quart rwc304 12"-very nice sounding, image dynamics 10"-best one i have ever heard, eclipse 12"-$150-sounded as good as my friends $300 eclipse aluminums, and a jlw3-sucks.
if you dont want to spend a lot i would reccomend the kicker comp vr, 2 8's or 1 10. you can get them for like $50 on ebay and they dont sound half bad. I would definately recomend an mb quart or a image dynamics.
but always listen to it before you buy it, we can give you tips and help but you really need to listen for yourself, and make sure in the store you bring your music in and listen to what you will be listening to in your car because that can make all the difference.
i also forgot, if you like to play it loud, there is a brand called memphis. they are decently price. they have aluminum tweeters but are pretty soft sounding. no matter how many times you blow them you can always bring them back and they will give you a new pair for free.