Nice they were quite popular in the W210 chassis based on the E420. Power development is according to a german collector which drives a Hagmann 6.0, a Brabus 6.0 and a MKB 6.0 (all in W210 chassis), the strongest of the other two tuners.
Hagmanns E60 was not only just raised displacement, but very often with polished intakes, portmatched of course and very sharp camshafts. They do know their job for sure. I would even take a Hagmann E60 before an AMG E60.