Obi100 at Amazon is only $40 up front and unlimited everything when combined with Google voice. No monthly fee for anything.
I use the Obi 110 with Google Voice. It will be free at least the rest of the year. I use Callcentric for the 911 service.
Ooma is great. I paid $220 about 2 years ago and am charged a fee of under $12.00 each year. I talk with a friend in Hawaii frequently. Clear as it can be. call me in Alabama 1 205 533 6196 to or give me your number and I will call.. Vonage is ok. I was paying $12.50 per month and decided to stop that payment.. before I ported my number. Vonage voicemail transcribes messages to text and attaches it to email. Ooma charges $9.93/ month for this service.