You're not going to find a HD monitor that's better than the LCD for focusing for under $1k. I use a Haier 7" SD TV/Monitor I picked up on eBay for $65 for studio configuration shoots. You can use it for focusing, although it's not great for that since it's SD. I mainly use it for color/framing.
Roderick, I too am very picky about focus, and also (because I'm getting old) have eyes that are not perfect. On my NX70 (which I have returned), I used these techniques to get best focus:
* Expanded Focus is a big help!
* Bought 2.5x reading glasses to help zero in on the LCD pixels
* Don't use Peaking - it is not as reliable as your bare eyes
* The viewfinder on the NX5 is the same as the NX70 - it is very sharp, and the diopter lets you dispense with glasses. I was actually able to get a better focus with it than the LCD.
Finally, if your NX5 does not have problems with back-focus, zoom in 20x, focus, then use that setting even for wide shots. (Test this before hand - if you have back-focus problems, this will not work).
Good luck and stay sharp!
Win7 Pro X64 on Dell T3400, MultiTB SATA, 8GB RAM Vegas 10e x64 DVDA 5.2(build 133) Sony HDR-CX550V