Hi Captain,
As timbersnoni said you can end up on many of the comparison sites by accident as they spider for content or through affiliate programs with Bizrate and others.
Froogle is something that's interesting oand offers a different approach, at present Google aren't doing much with this site, no doubt they have some plans, but it's free and you can either wait to be spidered or do a data dump into their system.
Perhaps

could hook up with Google to arrange a frequent dump of all

store products into the Froogle System?
There are a lot of Mall sites around and the majority of the good ones are Affiliate Commission driven. Ones that are based around a software platform as the common factor seem to fail as the Software is not recognized by the users, only by Merchants. The only mall systems I know of that work well are Amazon, Yahoo and Ebay Stores, which in effect, offer a Mall of sites, but they succeed in doing this through their brand not through the common software factor.
So in a nutshell i think the best route forwards would be that

partner with an existing system to feed our product data into them (froogle as it is free).
Cheers
Chris