Chris, like Sharad said, you could not go wrong with a Quintum.For the price, there are not many boxes that will give you better results.
When picking a channel bank to connect to a gateway, you may need a smart channel bank, the kind that will detect busy tones or reorder tones and supply disconnect signaling.
The worst trouble in many places is the lack of disconnect signal.
When a customer call into the gateway and finish the call, the port stay “hung” because the phone company does not provide any disconnect signal (remote disconnect supervision on the U.S.)
That will give you “hang” ports on the best case and wrong billing information on the worst case.
That is where a smart channel bank could help, but they are expensive.