FYI, I am currently running an i7-2600k, and I run 4-2MP and 1-4MP starlight camera and it is consistently running over 25%-30% CPU. It is fine for a starter system, especially since you have it (that was my scenario), but you should definitely put a 5th or 6th gen (or better) on your shopping list to locate and purchase in the next couple months as you will outgrow it quickly imho (it's a 2011 CPU after all so long in the tooth). You are missing out on multiple generations of platform improvement, and also 2600k uses DDR3 memory instead of newer DDR4 (and in another thread some testing has shown Blue Iris is definitely memory bandwidth limited).
Check out video from 2017 (at that time 2600k is already 6 years old). It is funny in that comparison it still shows the 2600k able to hold it's own against an 8700k in gaming (due mostly to offload capability to graphics cards). Also note about 9:45 the power comparison, the 8700k has lower idle and only slightly higher full load power draw (it also has 6 cores) compared to the older technology 2600k. Those power draw numbers aren't miles apart, but you will eventually save money (at higher performance level) going with the newer tech.
Secondly, I am running 11TB of surveillance storage and I get over 6 months of 24/7 video (but running some cameras at very low FPS), so your mileage will be much lower with just 2-2TB and higher MP cameras.
Thanks for all the great info. Right now, i'm just running the server test-bench style with the cameras sitting on top of the server. 3 cameras running at 4k resolution and 10fps. I'm sitting at about 30% cpu. For some reason, there ins't a display adapter showing under Device Manager, i'm suspecting that there isn't a intel graphics driver installed. I tried going to asus' website and tried to download the vga driver but the OS options only go to windows 8.1. i tried installing the 8.1 driver but it error'd out from the start. maybe i should try to the windows 7 driver. So my system isn't using hardware accelerations currently.
I'm currently trying trying to work out a price with a seller on ebay for an hp elitedesk g1 with a i7 4790 and 16gb of ram in a small form factor case. My only concern is that it only has 1 3.5" bay and 1 2.5" bay. I wonder if there's extra sata connectors on the mobo and i could just ghetto rig one to the outside if i need an additional drive down the road.