I am trying to upgrade my raspberry pi based NAS (with 6 HDDs) to a bit more powerful machine.

I use my it as homeserver for webserver, database server (mysql over LAN), NAS and much more (no gaming). Now I need to upgrade to a x86 machine for virtualization. I want a virtual machine host.

Please have a look at the end of my post for the parts list. I already had half of the items laying around, so it wasnt that expensive. I only had to buy the housing, mainboard and cpu.

But now my problem I started without any pci cards or sata drives attached to make sure everything is working ok.

When powering on, it shows a countdown for "Wainting for BMC initializing...". After 5 seconds, it continues to "System initializing".

But that's all. I cannot enter BIOS or UEFI and booting from usb or network doesn't work either.
What should I try next? I tried updating BMC firmware via the webinterface (didn't help), but I cannot update BIOS without posting. I do not get any splashscreen.

I dont know what the problem is and I hope someone else does.

Parts list:
Motherboard: ASRock E3C224D2I Mini ITX LGA1150 Motherboard
CPU: Intel Xeon E3-1276 V3 3.6GHz Quad-Core Processor
Memory: Kingston HyperX Fury Blue 16GB (2 x 8GB) DDR3-1600 Memory