Antonio's B&W photographs on his web are excellent. One reason -- I'm tempted to say the main reason -- is that he's careful to have the light right when he makes the shot. This comes across in his portraits especially. As far as post-processing is concerned, it would be awfully hard to beat the tweaks you can do with Silver Efex Pro.
I think you did what was possible, Jeremy, and it's quite good. I pulled the picture down and checked it in Photoshop with curves. It's possible to pull the lows down a tad and pull the highs up a tad, but I'm looking at a .jpeg, so the original raw file may permit even more improvement. You could grab the mid-tones and separate them, but if you do much of that you're going to kill the thing. I know there are photographers who, instead of grayscale seem to want black and white. Stamper tends to take his grayscale almost to that point and it's what he wants, though I don't necessarily agree it's the best result.
I'm as eager as you are to see what Antonio can do to improve on Silver Efex. His work certainly shows he knows what he's doing.
