Well,
The original system I proposed was a little over budget. But, the tweeters are very nice, the mids are quite composed, but they are a little boomy (not a bad thing for a door speaker). You won't find a much better sub than the Lambda even at 2-3 times the cost.
If you really wanted to upgrade in the future, the Bazooka amps are about the only thing I would be looking at.
The HU recommendation was just one that I originally thought fit the budget. The Alpine is an excellent choice.
If you know for sure that you aren't going to be willing to spend 450, I sent you a PM with an alternative.
I guess I just want to stress that the sub and speakers I recommended weren't recommended on quantity over quality. The quality of the drivers ranges from good to excellent.
