Acejavelin,
It looks like a solid option, but I have never installed one on a 5000.
I have had good luck with the Audiocodes MP-104, but it is setup as a MGCP on the 5000 if that makes a difference to you. This is also documented and was supported by Inter-Tel and as far as I can tell it still works well.
As for what not to use though; that would be the Quintum(Sonus) AFT-400 or any Quintum product as they do not integrate well with the 5000 due to SIP/SDP mismatch issues.
Thanks,
TE