This is a solution post. After fiddling a lot I finally got Omeka 2.0.4 to work in MacOS using MAMP (I tried XAMPP but had some issues). Here are the steps I followed:
1. Downloaded and install MAMP 2.1.4 [link].
2. In MAMP setup, go to Ports and select the Default Apache and MySQL ports (you don't have to, but it might simplify things).
3. In MAMP setup select PHP -> version 5.2.17. This is important (and the reason I'm writing this post) because this small change makes its so Omeka identifies the ImageMagick folder correctly later on.
4. Download and install ImageMagick. I used the one from this link. It installs ImageMagick to opt/ImageMagick and importantly, adds it to the path correctly.
5. Download Omeka and place the folder in the correct Apache folder. To check, open the MAMP program (in Applications/MAMP) -> Preferences -> Apache, and select the correct folder.
6. Setup the Omeka database (see details here). You can do this through phpMyAdmin by opening it up through MAMP. To do so, open MAMP and then click on "Open start page" - on the top you'll find a link to it.
7. After you finishing setting up Omeka (the procedures describe in the link above worked perfectly), enter as Admin and go to Settings. There, input your "ImageMagick Directory Path" as "/opt/ImageMagick/bin".
This worked well for me. I hope it might help others.