I'd say, if you can, make the decision to find an independent who is well reviewed and suits your needs (no agency) and use a forum such as this to send messages back and forth with that SP. Ask the questions and don't be afraid to give her the information as to your experience, your wants/needs, and what you expect.
There are sooooo many independent SP's out there that will communicate with you and give you the service you want. I find agencies are iffy... you may hit a home run but it's more likely you'll be tossed out at first!
good luck/donovan:)