[trancehead]

*this is one choppy ass post i realized, so ask for more clarification if im not clear as water

I'm no expert but heres what i picked up

i was doing the same sort of research a couple months back and from feedback ive read:
Wordpress and WP-commerce is just horrible for their free service, you pretty much need to pay to get anything workable with it
Same with magneto

So i went with Drupal 7 and commerce
Im no expert with themeing, so ive made a pretty bare bones e-commerce site with not too much work.
there are many modules with commerce that are necessary (such as shipping and all its dependencies, and paypal intergration) which are not included stock. so things like that have to be researched and fiddled with.

For drupal, the biggest thing holding me back from implementing some designs(themeing) is the fact that im not comfortable with Drupal itself yet. There are certain things to modify that are required to get the page to look a certain way. I can do some things, but not even to the stage where i am confident that it is the best way to approach it.

all in all, you need to deal with Drupal core, Drupal Modules (Commerce and non commerce ones) and themeing. I havnt dove into any of the PHP in depth, but i suppose for more complex functionality you need to make some changes which im not even sure how to approach let alone fully explain.

but seeing as you come from a programming background, ive taken C/C++/Java in university so learning PHP isnt too bad since u have a foundation anyways. this will let you do minor tweaking and maybe even the more complex stuff

you may want to look into Javascript and some frameworks (jquery, YUI) as its really important for the web now