Asterisk capacity panning

We are expecting some high call volume in new future, due to which want to make our setup ready. We are expecting around 1000 calls simultaneously. So my question is what should we add remove from the below list. Our goal is to handle the load efficiently and still want to have some backup capacity for around 25% more calls:

Sun Fire X-4140 1.6 GHz
12 GB Ram
350 GB HDD Raid 1

Software & Features to be used
Asterisk 1.8.x
Codec g711
Call recordings
Dynamic queues
Call spy & and blind-transfer
SIP trunk with provider
SIP user agents (Remote location)
AMI connection with ACD application