That's not an easy question.

Let me in turn ask you a Question or Two.
Not an easy Question that you are posing there.
Let me ask you a Question (Or Two);
How important is a PVR /DVR Function to you?
Do you have any short-medium term plains for HD (or DVB-S2).
The Dreambox runs on Linux and IIRC it can be made to fit a Laptop (2.5" HDD), inside it. Since it's Linux your not limited to using an External HDD via a FAT32 (<4Gib Max Filesize!).
If this *Linux OS* is also true with the Clark? IDK
As for the QBox, well that should be a Linux OS Receiver just like the Dream, I think you could modify it with a Laptop (2.5" HDD), as well but, I'm not 100% sure on that though.
In any case the biggest difference between the QBox and Dream, is that the QBox has a built-in Daiblo CAM in it, this means that you ~should be able to~ receive S*xV**W, on 13.0°E (et.al), and a few C*N*X Packages on 16.0°E, 09.0°E, and 08.0°W. Which you could only currently open up with an updated Diablo (Rev 2.3), CAM