Comparing the two processors, ARK | Compare Intel® Products , it is hard to imagine that the i7-4790k would have a problem, and that a 1st gen would perform better than a 4th gen processor.
Since they are different sockets, I would take a look at the motherboard you are using and make certain that the bios is updated, specifically since you are using a Haswell refresh processor. I would also check with ASUS regarding this issue.
Also, were you using the UR44 in the new configuration? Perhaps an incompatibility with the new motherboard?
I have the Asus Z97-A motherboard. According to PP at Asus (YouTube instruction videos) it is always worth checking the pins on a new motherboard, but I didn't do that, unfortunately, as I only watched the video yesterday. Anyway, the CPU passed the Intel Processor Diagnostic Tool okay so I would assume the motherboard is okay.
Thank you for your answer, which is the answer I wanted. I shall get onto Asus and go on the Cubase forums, but I'm hoping it will be okay on my second hard drive which I'm setting up as a DAW only system. If that doesn't work I'm hoping Asus will check out my board for me.