Move Windows Server 2008 R2 to a new hardware

configure the raid first then install your OS
use these links for your scenarios.  the instructions for server 2012 fall true for 2008 as well.

https://technet.microsoft.com/en-us/windowsserver/jj554790.aspx
https://technet.microsoft.com/en-us/library/jj134039.aspx

I would install Win2K8 on the new server, run DCPROMO, promote it to a DC, transfer all FSMO roles, change DHCP scopes to use the new server as the DNS server, change DNS IP address for all statically assigned computers, run DCPROMO on the old server, demote it,

If you virtualized it from the start, you could simply move the VM.  EASY and QUICK.

But since I don't think you did that, you can P2V the install - but if Windows CAME with the old server than you CANNOT move it.  It would be an OEM copy which cannot be moved.

Otherwise, you'd have to reinstall Windows on the new server and migrate from the old server to the new server.

Don't use RAID 5 on the new server. RAID 5 is a relic from the past and very unreliable, you only make life difficult with it. Stay with RAID 6,

Otherwise, as leew already mentioned, you can't move an OEM version of an OS to other hardware, it won't activate. You may be able to do that if you are in the EU or Switzerland, there you should be able to call m$ to get a new activation key, but in other countries/regions that won't work.

If it isn't an OEM version, then as has been mentioned, use virtualization.

I have the supermicro servers and the OS didnt came with them. I would stick with RAID 6 and I am planning to install VSphere Hyperv on the new supermicro, do a P2V of our existing DC and use it. I would shutdown the physical DC before i power on the virtual one. Am i thinking right? AM i missing anything here?

What do you mean with "VSphere Hyperv"? Either use VMware ESXi, which is vSphere", or "Hyper-V", which is the Hypervisor included with Windows Server OS's...

Also, even if the OS wasn't already installed on the server, it is still possible that you got an OEM version. OEM is cheaper than normal retail OS's, so if you got that and it is installed, you still wouldn't be able to move it to other hardware or a VM, unless you live in the countries I mentioned earlier.

Yes, i shall be using the ESXi. I just checked they are the OEMs. I remember that i performed a P2V on one our client server with OEM and i got a virtual key to activiate it on the vm.

You have just stated that these are OEM - you are violating licensing if you move them to another device.  We cannot help you do that.  Your answer in this instance is "You can't do that".  Sorry.  I suggest you purchase a Volume License so that you have the flexibility in the future.

I agree. Even i wont like to violate the license terms. I do have a VOlume License for Windows Server 2008 R2 which has never been used. Can i perform P2V of the existing DC which is running Win Server 2008 R2 OEM and during the activation of the virtual DC i can use the VL to activate. Or do i need to setup a fresh copy using the VL and then move AD and other stuff to the virtual server?

I suggest you try changing the activation code and see if it works.  From experience, MS only cares about how many licenses you really own and how many are in use.  I say this because I have been through MS license audits.

I am thinking of doing a fresh install of windows 2012 and then move AD to it. Also, we have roaming profiles and other application data on the OS drive. I want to make a safe migration without losing my data or AD. Can someone please provide me a step by step instructions. Thank you.