[SR-Users] Hardware requirements voip servers

Hello, We are considering upgrading our VoIP platform and I'm wondering what kind of hardware we need for our requirements. The architecture will consist of a SIP Proxy Server (Kamailio) in front and a cluster of Media/Application Servers behind it. The requirements are based on a single server. SIP Proxy Server: - Up to 100 - 300 calls per second. - Up to 5000 - 10000 concurrent calls. - RTP Proxy - Record-Route Media/Application Server: - Up to 100 - 300 calls per second. - Up to 5000 - 10000 concurrent calls. What do we need in terms of CPU, Memory, HDD when looking at the following specific requirements: - 100 CPS - 200 CPS - 300 CPS Which hardware components are critical for handling this many calls, is it CPU, Memory, Disk IO bound? Also which open source media/application server software is suitable for these requirements? We are currently using Asterisk, which works great, but perhaps there are others available which are more suitable for these requirements. Thanks in advance! Regards, Grant Bagdasarian