yes you could register your server as a provider at sipbroker.com and theis would assign you a number for your server, from there you would enter the extension number of your choice or whatever other number you have setup in inbound routing.
However if each extension has a number associated with it, then it may be easier to register the numbers with e164.org since the numbers you already use are easier to remember and that is all you would have to enter when calling sipbroker rather than the some code + an extension or psnt number.
Not only will it make it less numbers for you by registereding with e164.org but also easier for other people tryign to reach you as well.
Since you did say you had a block of numbers you would ike to register contact support directly...
Contacting support