Arq does not offer storage on the cheapest plan(I have no idea what you are paying for then), and even the $120/year plan only includes 250GB of storage. If I signed up with Crashplan I would upload literally all of my data to it - so 4TB of personal backups then.

Arq is actually a standalone (incremental encrypted) backup tool, though they are now also offering their own storage. Arq can be used with Amazon S3, Dropbox, OneDrive, sftp, Google Cloud Storage, etc.

E.g. I use Arq with my Office 365 subscription that costs me Euro 1.38 per month (four year academic discount) for 1TB.

Arq only runs on Windows and OS X though. I would prefer to use something open-source, that runs on Linux. I won't be renewing my Crashplan subscription when it expires.