Just my two cents, but Darty is the best website to check, as they list all their stock with prices (normally including delivery). But and Conforama don't seem to post their current stock online. You may also want to try FNAC. Their online service is supposed to be pretty good, though it has been a while since I last used them.

If you'll be in the Paris area, try surcouf.fr and lots of folks I know really swear by pixmania.fr for electronics and computer stuff.
Cheers,
Bev