Forum Moderators: phranque
"Atomz Search uses the power and speed of Web-native software to solve problems, answer questions or purchase products.
Second-generation site search products from Atomz deliver fast, meaningful search results to visitors while providing Web managers with insights into what users are searching for. More than 50,000 Web sites are using Atomz Search, including CBS, Palm, Macromedia, and The US Customs Service. The Atomz application network that underlies Atomz Search performs more than 40 million searches every month, all with greater than 99.9% availability."
The above quote is from Atomz.com whom I've used for roughly two years now and is highly configurable.
However, I can not attest to anything relative to those 50,000 files you mentioned. For accuracy sake, I'd suggest you view the site itself to determine it's applicational capablilities for your site.
Hope this helps.
Pendanticist
non-full disclosure - I'm not affiliated with SearchTools, but my company has a product listed there which would probably fit the bill.