We’re talking about Cubase and audio performances and you talk about display and resolution !
I recently upgraded from Win7 64bits with Cubase 7.5, to Windows 8.1 and Cubase 8 and everything is just fine. I didn’t compare yet the performances though.
I have 3 x 24" monitors including one 3D, one Sony 46" TV Full HD 3D monitor, and a Full HD 3D projector connected to the PC. A total of 5 displays, and my Nvidia Graphics cards are always totaly quite !
If your only concern is Thunderbolt, you can have it on PC. Have a look at Asus motherboards or their extension Thunderlbolt 2 card. This is not a Mac, but an Intel Technology.
And Dell makes some beautiful and affordable 27" and 28" (&+) 4K Monitors.
If you’re just looking for a pretext to switch to Mac, this is another story. Wether you like the UI, the design or else, there’s nothing wrong with that.
But don’t expect to get better performances doing so.