1. The distortion you are hearing is more than likely due to the fact that they are already blown. (why they were scrapped with the car)
2. You can't judge a product because you have heard good things form their brand name. Most companies make multiple levels of products. Some company may make incredible subs, yet their entry line leaves something to be desired.
3. You should be fine with a 4-ohm load per speaker on head unit power, but I would invest in that Kenwood unit asap if you plan to upgrade to aftermarket speakers.
From your level of experience, I would just look into drop-in coaxials as they are rather easy to install as a drop-in replacement. No separate tweeter/crossover/wiring necessary. If you are running stock now, you shouldn't have to worry about running a separate amp for your mids and highs to be satisfied.
If you have an ocd type of deal with running all similar equipment, and for budget, you could look into the Alpine Type-S base line. I run the 4x6"s up front now for temporary sound, not a single complaint. Great SQ for the average driver.
Alpine Type-S 4x6:
http://cgi.ebay.com/Alpine-SPS-500-5...#ht_2435wt_704
Alpine Type-S 6x9:
http://cgi.ebay.com/Alpine-SPS-609-6...#ht_2589wt_704
If those don't float your boat check some sites such as sonicelectronix.com and crutchfield.com. They are both usually running specials. Your best bet is to find something you like, then post up here for some extra $0.02 from the people here whom may have an idea. So many times people buy something they aren't familiar with and then ask for help AFTER it isn't what they wanted.
The saying is especially true when it comes to car audio. You get what you pay for! You are looking to spend at least $120.00 to make your car sound better than factory... Any other questions feel free to post up. I like to troll the audio section here every once in a while... lol