I think zen cart is good. Zen Cart admin has been hacked and the inbuilt email script is easily abused for spam.
zencart,magento is the best option.now it depends upon you which one you are choosing.
1 Magento http://magentocommerce.com
2 Avactis http://avactis.com
3 Google Store Gadget Google Store Gadget
Recommended!
If you’re just starting out, you may find Avactis’ GUI quite easy-to-use. It fits your $200. You can also pay $20 monthly.
There are many option out there and it all depends on your needs.
Personally prestashop and zencart come out top … magento tho nice to look at tends to be a little resource heavy,
Yes Zencart can be a tad confusing at first in its scattered file structure but i’d choose it over Osc any day of the week 
You also have x-cart, cubecart … to name but a couple
Personally i’d stick with open source software rather than a hosted solution from experience if you decide to move away from the hosted solution it can be a bit of a b*gger to get all of your databses out intact in order for a seamless move :), and there is always scope for improvement from the hoards of people working tirelessly to improve things from an end user point of view.
Rain
xxxx
From all the list of features you needed, I would say zenCart, or magento
I think magento can do any of the features right out of the box but you need a pretty good web hosting, NOT Godaddy, because magento need a fast hosting
I’m EXTREMELY biased of course …
But I noticed that not one post talks
about revenue enhancement.
The main thing we do with our product
design is to not only make things really
easy to use but to place a huge focus on
2 items:
1. Revenue enhancement - How do you get
more money from each customer. This is
really the difference between profit and
just getting by for many businesses.
- Create systems that give the small business
owner the opportunity to use one cart for
unlimited websites & manage them all from
1 login. Nobody wants to start over with all
new licenses, etc each time they add a new
website
…and the reality for most small to medium sized
businesses is that they do run multiple websites
or they plan on running multiple websites.
How many websites you think you may eventually
have in the next 5 years really needs to come into
play in your decision making process as does
up sell, cross sell, sales bundles, etc.