Suggestions welcomed

I’m thinking on installing an IP PBX for a medium size company. I have almost all figured out but as I’ve never done an installation this large I’d like to hear some suggestions from your experiences. I’m in Argentina so take into account there are some budget and parts availability issues to consider.

  • The PBX will handle around 50 - 70 IP phones (Mostly Polycom 301, some Polycom 601 and some softphones). It should also handle a small 6 seat Call center. There will be around 16 inbound analog PSTN lines. Max concurrent calls: 15-20.
  • I was thinking on installing two identical replicated servers. They will be based on Intel S5000SVA server board with 2 Xeon2.66Ghz, 2 250GB SATA disks in RAID1, 2GB RAM and 2 GigE ports. 1 Digium TDM2405E (20FXO + echo cancel). Does anyone know how these boards work with CentOS/Asterisk?
  • The network consists of a 48 port Linksys SRW248G4 and 2 24ports 3COM superstack3 switches (located in different areas). Traffic will be divided in two VLANs (Data and VoIP). So far PoE is out of budget but servers and switches will run under a UPS.

What do you think of such a system running Asterisk/Trixbox. Will it meet the requirements and handle the load of calls. I know these questions are difficult to answer with so few details but anyway I’d like to hear what you think.