Your wife's gold tip Nugent 500 arrows are 8.4 GPI while the 400s are 9.3 GPI. That amounts to 23.4 grs extra weight then add the extra weight for the 125 gr tip and just for a gesstimate if your wife's bow has an IBO rating of 300 fps (70# @ 30") at 26" it is currently launching an arrow at 189 fps, with the increased weight it should be shooting about 173 fps. Calculating the shaft weight plus components and broadhead the 500 come in about 413 gr. The 400s will come in about 461 gr.(these are approximate but pretty close based on a 26" arrow).
(ref: http://archerycalculator.com/estimate-bow-speed)
The kenetic energy for the lighter arrow should be 32.7 ftlbs and the momentum at .346. With the heavier arrow the values would be 30.6 and .353.
(ref: http://archerycalculator.com/archery...um-calculator/)
Although KE is an important value you must also consider momentum. The heavier arrow even though it is moving slower and has less KE should give greater penetration. I'm not sure it the set up will still provide a complete pass through but it will increase the odds.
BTW thank you for your service. We at home are honored by the work you and your fellow military do for us.