I'm going to let this hit before I decide on picking it up. It's not the same devs, its a mini series, so I have some reservations.
LIS 2 is in production also. So we'll see.
I play at 1440p but have streamed the odd time. Mostly I stick to 1080p as 1440p streaming was fairly demanding even on my i7 4790k/970 machine.
I've recently used Mixer streaming built into Windows 10 and it seems to be 1080p without option to change.
Thats one old CPU. I did a quick look for you but couldn't find any motherboards on sale anymore. Maybe someone else would have better luck.
The machine might be a nice Media box/server if you throw on a lightweight Linux distro.