Here is some threads to read for w124 spkrs:

1. http://www.peachparts.com/shopforum/showthread.php?threadid=39815

2. http://www.peachparts.com/shopforum/showthread.php?threadid=30314

It' really hard to say. I've listened to the infinity's and they sound pretty decent off of deck power. Quarts will be bright firing off the windshield. There is tons of other smooth all around 4 1/2" speakers like Diamond audio, JL Audio, etc. You just need to keep in mind that what they sound like in the showroom firing at you is not realistic in terms of what they'll sound like in your car firing off your windshield. Also of course lotsa people on here have installed the rainbow speakers that drop in, so that is also an option though i haven't heard them.

My recommendation if you can fit them, JL Audio XR400 CX. A bit pricey but they sound tasty and are a pretty tight fit for the 124 dash.

good luck