Securing the Server Farm

["WALI" <hkhasgiwale () gmail com>]

We are in the middle of designing a Network Infratstruture and was wondering 
what's the current design improvements I can undertake in designing the 
Server farm. Given that there would a Core switch(two for redundancy) and 
IDFs for connectiing at the edges. How should I place my servers (about 50 
of 'em).

Should I place them directly on the core and build some L3 access lists or 
put another set of L3-L7 switch after the core and connect all my servers to 
it?

Can I place an IPS/Firewall in the middle or would that be an overkill?

Pls advise!!