shang308 fxo gateway + trixbox for SME

I just finish such a case for a small company.
the hardware is shang308 fxo gateway and a pc with trixbox run on vmware player.
2 CO line , one for incoming call, the other for outgoing call.
Even there are other PBX cheaper than $10, but they still use this system. it is just because their saleman can receive calls to their extension by their mobile phone.