I have no idea what 6x9's are the best, but when I bought my first car I bought the cheapest 6x9's that halfrauds were selling at the time. And the cheapest MP3 playing headunit with a 4x50W power rating - which was a JVC. The speakers were £35 blue JVC jobbies, rated at 250W or something, but DOOD they sounded great. The main cone was rather flimsy which, I suppose, made them easier to move, making them very punchy. And the treble always sounded very crisp and clear. I don't think any 6x9's offer outstanding bass, and I was never able to compare them against any other 6x9's, but for the price I could not fault them at all. In fact, I miss them. ;) The system in my current car has two 12" subs and some 13cm co-axial speakers is definitely a lot bassier, but it lacks mid-bass PUNCH and doesn't sound as clear the system with the 6x9's. As for the head unit, I'd just pick something that has all the features you want. Any head unit from a decent manufacturer will sound fine in a car, because although more expensive unit may have better specs, I'll be very hard to hear the subtle differences over the road noise anyway.