You didnt mention OSCommerce. Good. Dont bother. I dont like their coding and query style and it is definately not a very scalable product. I have had to make some hacks to their inneficient code to keep them from crashing a Glowhost customer with thousands of inventory products. Not to mention, they took forever to be compatible with mysql 5 (if they even are now!)

I see CS cart makes specific note of easily handling 10K items.

Also saw a product OpenDNS - supposedly designed to scale, but site is down, writers can't spell, and so probably a bit on the scarey side.