Vote here for CrashPlan Pro. I've recommended it to half a dozen companies now and never had a complaint. It's fast, reliable, compatible with Mac/Windows/Linux, the Linux client actually *works*, pricing is very fair, and you get the option of unlimited storage with per-machine pricing or unlimited machines with per-GB pricing. Bonus: Their website lets you input your number of computers and total storage requirement and suggests the cheaper plan.
I've only had to use their support once (regarding VSS compatibility issues with a Counterpoint POS database) and they couldn't resolve the issue but were courteous, responsive, and technically proficient.
Finally, unlike certain competitors (*coughCarbonitecough*), Crashplan doesn't charge a crazy server tax. My primary company pays $10/mo to back up around 300GB of data from a Windows Server 2008R2 DC. Backs up to a USB hard drive as well as Crashplan Cloud and works like a charm.
I've only come across two use cases where Crashplan isn't the preferred option.
a) Certain database/POS systems, Counterpoint in particular. Crashplan uses VSS which has compatibility issues with some databases. Crashplan can operate without VSS, but then of course in-use files don't get backed up which can be a disaster on a DC. We ended up migrating Counterpoint off the DC to a dedicated box (good practice anyway) and using ShadowProtect through the Counterpoint vendor in this case. Crashplan Pro covers the DC just fine in the absence of finicky databases.
b) My personal setup, where OneDrive is just what the doctor ordered. I sync about 150GB across 4 PCs and OneDrive matches my workflow perfectly. It only offers versioning for Office docs, but that's all I need.
Hope that helps!
EDIT: given my glowing recommendation, I should probably state that I get no kickbacks of any kind from Code42/Crashplan. I'm not a member of any affiliate program; just a happy customer.