@kjl1065 If you are planning a balanced line preamp, its a good idea to ask if the balanced preamp supports the balanced standard, AES48. The reason this is important is the balanced line system has several goals amoung which are elimination of ground loops and elimination of interconnect cable artifact. For the latter, if you've ever auditioned cables and heard a difference, that is what I'm talking about. Imagine not having to worry about cables again...
These two benefits are lost if the balanced line standard is not supported by the preamp. Most balanced preamps I've seen don't support it; I think the reason is to reduce cost, or else the manufacturer may not be aware that there is a standard.