Need to get more info on mods before making a purchase decision

[Zookie]

I wish to create a community area on my web site that is composed not only of a forum but also an area that members can upload and download files they wish to share with other community members. I think I can do this using vBulletin and a mod but need to confirm it before I buy a license. Here's what I want to implement:

- Users would to need to register with the community and be signed in before they could upload or download files. So the vBulletin authentication would be used not only for the forums but also for the download area. Visitors could browse files but would need to be signed in to either upload or download files.

- Users would be able to search for lists based on file name, a short description field for each file, user who uploaded the file (for instance, search for all files uploaded by vBulletin user XXX) and file category. Visitors would not need to be signed in to search but they would need to be signed in to download what they find.

- The files themselves would be stored at a location on my server that can't be linked to directly. In other words, one couldn't email someone the link to a file. All downloads would have to be from the download area on the site and only available after signing in.

- I'd want to be able to at some future date change the storage location of files to a different server (such as Amazon S3 storage) without having to make any major changes to the structure or implementation of the download area. The links wouldn't change - only the implementation of where the links transferred the files from.

I've found three mods that might get me where I want to go:
- Links and Downloads Manager
- DownloadsII
- BFC-Download

My problem is I need more information. I have specific questions I need to ask about the mods before I can conclude that vBulletin + one of these mods is the right way for me to go. But I can't post questions in the threads for these mods because I don't have a vBulletin license. So I'm stuck. Requiring that I first buy a license before I can post questions (the answers to which will determine whether I want to buy a license) is putting the cart before the horse. Any advice on how I can get answers from the respective developers of the above three mods would be greatly appreciated.