libvirt users - May 2015 - Hardware requirements for SPICEd desktops

Hello,

I posted the following to the kvm list yesterday, but now I suspect this 
is a more appropriate place to ask...

I'm considering to build a new server and to use SPICE protocol to 
deploy all the Windows guests to the local network.
It's my understanding that:
1. I should create the guests on the server
2. I should use remote-viewer on a minimal desktop linux on the clients 
over SPICE protocol
3. I should enable QXL on the server
4. I can get clients USB ports and soundcards working in the guests

Now, assuming I've understood the above correctly, I haven't understood 
what are the hardware requirements server and client side:

1. Let's say I assign 4GB of RAM to each guest and that the network has 
20 running guests at any given time, should the server have at least 
80GB (20 by 4) of RAM or can I "oversell" a bit and bet on the fact
that
only few guests will actually use 4GB?
2. What's a reasonable amount of RAM to have installed client-side, for 
4GB-RAM guests?
3. Should the clients have a CPU that supports VT-x?
4. Is it possible to have QXL supported on the clients regardless of the 
physical video adapter installed?
5. And what about the soundcard support? Will any linux-supported 
soundcard do on the clients?

I wrote:
> 1. Let's say I assign 4GB of RAM to each guest and that the network 
> has 20 running guests at any given time, should the server have at 
> least 80GB (20 by 4) of RAM or can I "oversell" a bit and bet on
the
> fact that only few guests will actually use 4GB?
I've found the answer to this question: https://goo.gl/FFVYr3
> 2. What's a reasonable amount of RAM to have installed client-side, 
> for 4GB-RAM guests?
> 3. Should the clients have a CPU that supports VT-x? 
> 4. Is it possible to have QXL supported on the clients regardless of 
> the physical video adapter installed?
> 5. And what about the soundcard support? Will any linux-supported 
> soundcard do on the clients?
After having installed a test drive guest at my home network, I suspect 
I have understood a few things. I think the client needs only the 
minimum resources to run remote-viewer, but:

1. If the client has a linux supported video adapter, and the guest has 
the spice agent installed, then the guest OS can handle hardware 
accelerated video playback in remote-viewer.

2. The client RAM is never used for the guest OS processes

3. It follows that hardware 3D acceleration is meaningless in a 
networked environment, because the client video adapter would need DMA 
to the server RAM over the network, which would be least very slow, if 
not impossible at all.

Am I correct?