The guys in the office across the hallway have a very robust and easy to use CMS with shopping cart add-on - they will also customise for individual requirements if necessary - not cheap but solidly built (PHP,XML,XSLT) and easy to use.
http://www.featurecreep.com/products/ - CMS
http://www.featurecreep.com/products/features - add ons (incl. shop)
As a side issue - did you find cubecart worked fine up to 10000 products?