We used to use Lemonstand but they are killing version 1 and version 2 is hosted only with outrageous pricing based on inventory (at least at prices our clients would not pay).
We have currently settled on
CS Cart for the eCommerce end of thing and of course MODX for content. It has some nice multilingual features.
No eCommerce system is as nice as MODX (at least that I've run into). A fully featured eCommerce module within MODX would be the killer module for it. But eCommerce is an entire world on it's own and building a standout module would be extremely time consuming and take many hours of development.
eCommerce systems are lacking on the CMS side and CMS's are lacking on the eCommerce side. Whichever CMS/CMF marries the 2 will be very popular.