Remote Mark,
It sounds like you are putting in a pretty decent system. I don't know the output of your amp, but knowing the quality of MB Quart, I would highly recommend putting in speakers of a bit higher quality than the rainbow ones. If you put those in, they will definitely be the weakest part of your system.

This is just my personal opinion, but I would suggest putting in some lower end MB Quart or Alpine (or any other company that is comparable with them) speakers. I just think it would be a shame to go to all the work of installing an amplifier and then use it to power speakers that are below its capabilities.

Thats my $0.02

Quick Question:
Someone above noted that they fit 5.25's in their dash. I have a 1995 E300, and I know that the stock speakers are something like 4.75" and I was wondering how much work it took to fit 5.25's in there.
Thanks