MBP late 2013 i7 2.3gHZ restart problems and major input lags

Question

Since I've updated my MBP i7 2.3 Ghz late 2013 to OSX Yosemite (10.10.1) I can't restart the macbook with my promise harddrive and apple cinema display still connected via thunderbolt. When I restart it keeps hanging on the grey screen without the apple logo. When I unplug the thunderbolt and usb cable, hold down the power button and turn it back it everything is fine. Just the restart won't work.. Any ideas?
Further more, I receive major input lags in different programs. For example I use Final Cut Pro (10.1.3) a lot for my job. I use managed media library all stored on the promise harddrive via thunderbolt. The footage I use is raw of the SD card from a Nikon D800 (h2.64 mov), of course i let everything import first before editing. Though I get major input lags (0,5-1,5 sec) when pressing the spacebar to play for example. Ive used this workflow exactly the same on my previous MBP (17" late 2011 I think) without any lags.
Specs of my MBP:
MacBook Pro (Retina, 15-inch, Late 2013)
Processor 2,3 GHz Intel Core i7
Memory 16 GB 1600 MHz DDR3
Graphics NVIDIA GeForce GT 750M 2048 MB
Storage 512 GB SSD
Hope anyone can help me.

Answer 1

Your original configuration is an HDD. Have you considered replacing it with an SSD. It helps quite a bit.
The current 2013 (and now the 2014) MBPs are excellent machines, and can run Bootcamp via native EFI (Win 8/8.1 - Win7 has some driver challenges), rather than the CSM-BIOS layer and you will get very good performance. I would recommend a 16GB MBP. If you do a lot of external display work, dual GPUs may work better for you.
I use the TB-to-FW for accessing external disks, not sound cards, but the storage works fine. This machine can support 8GB RAM, which may also be worth considering.