Best Multi-db setup with 4096dbs, Amazon S3 and / or extra hard drive

My database is finally sorted out and we are ready to rescale to 4096dbs with multi-db.

I want to know what the best or recommended setup would be on my server.

I would like to offset uploads or db's on a separate hard drive or possibly work with a CDN like
Amazon S3.

Not sure if that is advised.. What would be the best way to set this up?

Thanks again!