Have had experience with Silverstone Group. For the right price, they will tell you anything you want to hear, IMHO. Take this report and $6 and you can get a nice coffee at starbucks.
"NOT CREDIBLE UNLESS YOU EXPLAIN YOURSELF FURTHER!"
Golly, since you responded in all caps I reckon I'd better answer!

I was integrally involved with a project where Silverstone was the consulting group. Their "direction" changed multiple times based on what different leaders wanted to hear. Beyond that, there are ongoing activities that preclude me from commenting any further. If that means I'm not credible in your eyes, I suppose I'll still sleep OK.
I'm not rebuttling just to play Devils advocate, but if it's what different leaders wanted, what else are they supposed to do after that many change of directions? It almost sounds like a leadership problem from the organization they audited. Or is there something more to it that you haven't had the chance to explain in detail yet?
Second, you're not the first person I've heard explain a story that silverstone hasn't lived up to their name, thus dropped the ball on a client.
Third, I helped pry a nice sized account away from them a couple years ago and saved a client $10-$20k per year.
So, my overall point is, I don't disagree with your statement about silverstone overall, but your particular situation would take more detail for me before I discredit their audit process. Sometimes I've learned, when as much as you try to sell a service the right way, no matter how true you try to be your customers, you also sell to your client what they want because they won't listen.