Manoa- welcome to the forum! I've been using Kerastase products for a while now and while I'm a bit of a beauty product junkie and always love to try new things, I always go back to Kerastase.. I just get consistently great results from their products. I alternate between the Volumactive and Bain de Force lines to help give my thinning hair a little extra strength and volume. Have never tried the Aminexil... I'd be a bit skeptical about its ability to prevent hair loss, but it's probably still a pretty good product that might help your hair look and feel healthier.
Never tried Phyto products myself but I've heard good things... again, it's probably something that's just going to help improve appearance... give your hair strands a little "oomph".
I just started using Rogaine 5% yesterday (eek!), so we'll see how that goes.
Good luck and peace
S