Your 125w is providing a nice temperature gradient, but the mesh is probably intercepting quite a bit of the UVB. I have the same mesh top for mine, but I don't have one of those bulbs to test out, unfortunately. Generally you'd want that bulb at around 10-15'' above the basking area for optimal UVB output. With the mesh top, I'd guess that is cut down to about 6-12'' or so. Since you have the fixture on a stand, you could remove the mesh top if you don't have any other animals in the house. I have the 18'' tall version of that tank and just leave the mesh off of it. If you can get the bulb within those ranges and still provide a good heat gradient, that bulb may do the trick.
Another option as mentioned is to move to using a UVB tube along with a halogen or incandescent light for heat. The advantage is that you can set the
UVB light at the appropriate distance and adjust the heat separately. In this setup I'd probably use a T5 fixture with a ReptiSun 10.0 or Arcadia 12% bulb. If you put the fixture right on top of the enclosure, the mesh should cut down the UVB so that it is appropriate for the distance to the basking spot. Then just use the hanging fixture with a halogen flood light and adjust the height until you get the proper surface temps. The Solar Glo could then be used in a clamp fixture or second hanging fixture somewhere around the house to provide UVB and heat during free roam time.