I am looking for a list of 10-20 eCommerce mid-tier shopping carts
with the largest install base of customers. Hierarchical order
preferred.  Cite sources please.

By mid-tier I mean:
1)  Something other than a point-and-click shopping cart.  

2) More specifically, a mid-tier cart gives the webmaster the ability
to add javascript code to their pages and to modify the order
confirmation page to output a value like the order reference number.

I will holdout for a list of products that meet the second criterion,
but will pay for a list that satisfies only the first if time runs out
and my ideal answer has not been found.


I don't want to waste anyone's time.  If you are unsure whether you
understand what I am looking for, please don't put alot of time in. 
Either ask me, or do a little bit of answering and post it for
clarification.

Thank you anyone who answers!