I would say that you should go with the 3750x series or atleast the 3560x series.
why the 3750x ? stacking! both powerstacking and datastacking.
the powerstacking is a very nice feature ! and the datastacking gets you loads of speed.
and well if you buy the x series then you have the limitedlifetimewarranty.. that is not a bad option.
The me3400 (wich is the ones I am guessing you are looking at) is not for you. they are for fx ISP and so on.
the metro ethernet access does have some differences than your average cisco 3560 switches and will not sit well with your normal lan configuration.
and well to get gig you would need to get the 12port version, ie the me3400 is not an option for you.
so well how do you want this ? and how big is it ?
we are missing alot of information such as do you have internet access and so on.
where is the backup going ? (to another building, city, country , far far away.. )
how far between switches and so on..
How much data is generated ?
will the chokepoint of 1gig be enough in the L3 to send data between the different vlans/l3 ?
As a general point I would setup a l3 device in the middle to cope with most of the traffic.
and separate on l3.
Dependin on how big/much the backups are I would setup a special network just for backups.
(backups can realy consume bandwith depending on how they are done)
and I would set the network up something similar to the first picture you have.
but do not forget about the network flows, ie how is the information going to flow so that you do not end up with huge boittlenecks somewhere.
as a general rule I would buy the same type of equipment, the fewer models the better,
if one or several breaks down in the core then it is possible to replace it with units from the edge if they are all the same model and license.
less testing of different softwares and so on..
and always get atleast one spare.
Also i see no firewalls in here, if you have access outwards its just prudent to setup firewalls.
Good luck
Hope this helps..
