I'd go with the Small + 100/45 if I were you.
You could also go with the Small + 110/75, and ride it with no spacers. That would get you a little closer to your current base bar stack. But personally, I think the tall stems are going to look a little funny. Avoid if possible.
Going to a larger frame would be possible, but isn't totally advisable. You're a great fit on the Small frame with the 100 stems, because they place you right in the middle of their range of pad reach. If you ever need to move your fit numbers, you're better off in the middle of a range, than on the fringes. These bikes are going to handle fine with either the near or far stems. The bike has a slack-ish head tube to help with that, and none of these stems are extreme, assuming you don't move your pads forward another 40mm.
Of course, Carl may tell me I'm off my rocker ;-)
The Triathlon Gear Guide