Volume Licensing and KMS questions

Question

I've been reading up on MS licensing all week and still slightly unsure of what we need.
We are revamping our infrastructure and need new licensing. We have 150 Win 7 Pro OEM (and some Win 8 Pro OEM licensed  computers that have been downgraded to Win 7 Pro OEM) computers and are getting 4 physical Windows Server 2012 R2 Standard servers.
We would also like to add some virtual servers to those.
From what I've researched, we can just purchase a single 
Microsoft®Windows®ServerStandard 2012R2 Sngl OLP 1License LevelC 2Proc
for $865 (used quick quote from MS website). This will give us a KMS host key to install on a 2012 server. We can then reimage Win 7 Pro and other 2012 servers and they will be able to activate with KMS.
Is all this correct? Or do I need to purchase separate Server 2012 and Windows 7/8 VLK's?
I read somewhere that this will also grant access to ISO files for imaging that already have the KMS client key or do not need a key at all? Or can we take any Windows image and apply the corresponding KMS client key to it and use that for imaging?

Answer 1

We are going to end up re-imaging all of our machines, current and future, anyway. I should just be able to use any ISO to create an image and implement the KMS client key there or during deployment, yes? Not gonna buy a client license just for an ISO that
I don't need.
Is software assurance recommended? I saw an advantages chart of it and noticed it included new product versions, license mobility, and virtual desktop allowance, but not much detail about what each of these means exactly. It seems to be something we'll probably
want though.
reimaging rights, can be a little tricky:
http://www.microsoft.com/licensing/about-licensing/briefs/reimaging.aspx
Here is an overview and some scenarios for customising/reimaging:
https://technet.microsoft.com/en-us/library/ff730914.aspx
Note that there are some limitations about customising if you *don't* have a VL agreement..
SA benefits:
http://www.microsoft.com/licensing/software-assurance/by-product.aspx#tab=2 
There are many benefits to SA, but the value of each benefit varies according to your organisation.
It's also worth noting that when you purchase a product (e.g. new computers with OEM Windows license), within 90 days or purchase you can enrol them in SA, and I think that might be less expensive that if you attach SA later on. But you'd want to consider
that you'll get your value from doing that, compared to some other agreement approach. There are lots of ways to bundle things up to get discounts, many different offerings across different licensing programmes.
Don
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