Own hardware solution?

[SparkyRih]

So I'm an entrepreneur who's starting a new store (selling smartwatches) as an extension to my already existing webshop. However, my main occupation is in software engineering, and I have a background in system administration. So probably to your surprise, I'm doing all the tech stuff myself

I've been running ESXi servers (in actual DCs) for years now, and I'm currently waiting on a Core-i5 mini PC from China to throw pfSense on to use as my main router for the store/office...

I do already have a professional certified alarm system installed, but I obviously also need video surveillance... "Professional" solutions are waaaay too expensive, Chinese solutions, well, I'm not sure if I should trust that software, so there is only one option left: Building my own system based on an open source platform!

So my question to you guys, what hardware would you recommend to me for running ZoneMinder?
- I'd like to use Ubuntu as my OS
- I'd like to use about 8 2MP/3MP 30fps camera's (I'll find those myself)
- It shouldn't be too expensive, but also not too cheap (since I'll be using them professionally, I'd rather use some overkill hardware of course)

Any advise in existing systems? Or better yet, maybe I can harvest components to build something awesome myself?