I've been happy with unmanaged servers from Incero. Their severs use ECC RAM, their support seems competent, and they offer buy-down prices for things like RAM.

Back to pgrove's point, though — there are trade offs with using a dedicated server. The storage isn't as reliable as S3 and the server itself is likely less reliable than a VPS (since some hardware problems on a VPS can be solved by migrating to new hardware and only involve a small downtime, rather than the large downtime of restoring from backup).

A major advantage to dedicated servers that I don't hear much about is simplicity. Dropping everything on a dedicated server means I can use local services like the file system rather than having to deal with S3 and latency and bandwidth costs.

Edit: I just realized that the idea was to use Rackspace files + one of their servers rather than S3 + EC2. Somehow I missed that bit and was thinking about just storing everything on the dedicated server.