How much computer for Proxy

I would like to setup a proxy server for my network. Is this enough computer ? any suggestions on how to go about selecting the right h.w. ?
The computer I’m hoping to use is a:
Dell Poweredge 1400SC
933MHz
133MHz front
32kb Level 1 cache (16kbinstruction cache & 16kb two-way write-back data cache)
128mb 133MHz SDRAM
18gb 10,000 rpm Ultra3 SCSI h.d.
Embedded SCSI controller Adpater
NIC Embedded Intel PRO/100
second NIC PRO/100
330 watt power
For 25 Win2000 clients on a NT 4.0 network which include 4 NT servers, all using a T1 Cisco 2600 router and two 3Com 3300 switches.