Hi,
i have done all this many times for different companies (TRG, Blaze digital,VnD Solutions etc), for Ip Phones cisco 7940, 7960 is best for asterisk and we have to change its firmware for SIP, for Buildin Sip phone polycom IP 430 is best. voicemail can also be get on web. conferencing solution & call recording and CDRs also be given in same price. Call Routing and basic support training will be given to you.