Final update (for now)...

We have seen that the dedicated hardware still isn't powerful enough to do 64 players on 60Hz on all maps, while our Chain Link with 48 players was doing really great on the same machine.
So, both our servers have been moved back to their original location since this morning.
At this time our provider cannot offer us better hardware against reasonable costs, so running our CQ server on 60Hz will not happen any time soon. Unless the coming winter patch (which is only a few weeks from now) makes a huge leap forward in CPU optimization, but I doubt that.
The good news is that our Chain Link server will stay on 60Hz, since 48 players on 60Hz is kinda behaving like 64 players on 30Hz.
So the hardware can handle this just fine.