• I have 10 clients with Windows 8 Pro edition (planning to upgrade to Windows 8 Enterprise if required.)

• I have 1 server with 16 GB RAM ; i5 3rd Gen ; 500GB HDD ; Windows server 2012 DC edition.

• Now I want to have Excel files over the server , and 10 clients being able to access the server at the same time using u/n and P/w to access using some software or DirectAccess.

• All 10 clients can work over same sheet if they want (We can achieve that using Sharepoint 2010)

So the question here I have is how to do all that ? Where to start, what exact version to use for office, SharePoint, Windows? And how to configure them up to work as I want..

Seems like a very straight forward one other than some tricky part: version of SharePoint to use with Windows 8, how to achieve multiple checkout in SharePoint library, etc.

Solution:

On the server, you can install SharePoint 2010 and you can use office 2010 on client machines. If they already have office 2013 with Windows 8, no need for this.

1. SharePoint installation guide can be found here http://technet.microsoft.com/en-us/library/ff607866(v=office.14).aspx

2. Use office web apps for browser compatibility for office documents. 

3. Create a document library with version enabled and put your documents. You are good to go.

4. But there is no multiple checkout, merge feature in SharePoint.

We have two ways to get this working:

Co-authoring is a feature which can substitute to this which is available in SharePoint 2010/13 which is available for Microsoft PowerPoint 2010, Microsoft Word 2010, and Microsoft OneNote 2010 documents. But you can use Excel web app for co authoring and attain this functionality. See more details here http://office.microsoft.com/en-001/sharepoint-foundation-help/document-collaboration-and-co-authoring-HA102772333.aspx

Another available option is to use SharePoint Workspace and work online and merge when you are done with editing. You can see working with SharePoint Workspace which takes documents offline and syncs when you go online.
More details here- http://blogs.msdn.com/b/sharepoint_workspace_development_team/archive/2009/09/30/sharepoint-workspace-2010-the-new-stuff.aspx

Now just before we conclude, one more question: Does Windows Server 2012 support SharePoint 2010? 
As of now No.

See details here http://support.microsoft.com/kb/2724471
We need to wait for service pack2 of SharePoint 2010 to install it on Windows Server 2012.

So overall, for this setup, we need to have SharePoint 2013 and Office web apps on the server and use one of the above mentioned functionality for multi-user checkout and check in.