You'll find the rate question to be the most difficult to answer. Some providers are fantastic on termination but expensive on origination... and vice versa. Others have inexpensive origination but high monthly DID fees. Still others have monthly minimums. Good luck!
We have been in trials with several carriers after deciding to leave Broadsoft. We selected Bandwidth because Broadsoft did - good endorsement. We had a great trial with V1VoIP and Flowroute. Bandwidth tried to do some weird big boy power play and their rate contract is indecipherable. They basically said unless you will sign a contract for $5K in monthly revenue we wont be bothered to set up a SIP trunk for you to test. Really? Bye.
The sales guy I was working with said he gets a lot of negative feedback about their "We are Bandwidth.com, you know who we are and we don't need to prove our service with trials" attitude. I don't need a partner like that. Lots of options out there.