Best VOIP Provider in US?

Hey Asterisk Users,

I am looking for 2 voip accounts in US, 1 for outbound calls and 1 for inbound calls with following requirement :

  1. both the account should be able to register with asterisk PBX.

2)the voip account for outbound calls should be able to make 100 concurrent calls.

3)the voip account for inbound calls have DID as some special service numbers eg. #250 or 800.

Please help me with a name of good provider with best rates as i m looking for large volume of calls.

Thanks in Advance