I have an Asterisk box setup at a business. No amount of tweeking has been able to get consistantly good conversations via the VoIP providers. So, the owner wants to keep Asterisk but switch back to landlines. What is the recommended way to connect them into the Asterisk box? I have used Digium’s TDM cards before but they are a bit pricey. Is that still the best way to go or are there other options??