Well first off, having more power will help in controling the speaker. In that I mean the speaker cone will be able to move out (linear) and return to its original position much quicker with more power. So this will help alot for rock songs and electric that have quick fast beats. You will definatly enjoy the increased power. I noticed crisper highs, and much more midrange bass.
I think your best bet would be to 2 channel the tweets and 4 channel the other speaker (given you know what active is). If not this may not be the route for you. IN this you have to set your gains to the tweeter so that it doesnt damage it by distorting the signal. If you distort the singnal to long, you wont have tweets anymore. You may want to think about purchasing a good compnent set after selling your other equipment, that way you have a passive crossover and something easy to amplify. You also wont have to set freq points for both the tweet and the midbass. From what I understand, each and every tweeter and midbass driver has its own specific freq ranges to extend to, this goes just as importantly for the power setting, so unless you know alot about YOUR specific speakers, active may be a very hard thing to do.
According to your specs listed on the sites provided. You would need around 80 watts RMS to power them. Elementaldesigns.com has a 4 channel that does 85x4 and is AB class, so that would work well. As for the tweet amp, you have to look a little more specficly to find power rating's for them, but to be safe I would say around 50 watts would be plenty, if not less.
To be perfectly honest though, I think your jumping into something you are still a little unaware of. I'm not saying this to be mean, I don't know barely anything either, but through reading and gaining knowledge from a few people here I have found out alot of useful info when it comes to car audio.
http://www.bcae1.com/
^ This site should give you good basics of car audio. As well as some things you may not know. Took me forever to read most of it, but I find it was well worth the time.