We tested the Victory arrow in nearly eveery crossbow out there. They do fly very well in the Parker, Ten Point and Excalibur. All the testing on those three bows is complete. I think we have found the best arrow.
The Gold Tip Laser II is a tough arrow to improve on, but I think we have. The reason I like the 100 grain heads is because we build our arrows around a 100 grain head, no other reason. If the 125's fly good I wouldn't change them.
The problem likely isn't with your arrows, but rather the arrows forward of center. Think of your arrow as a dart. You know why darts fly so well? It's the weight in the front of the dart. If there would be more weight in the rear of the dart you couldn't hit anything with it.
I've got a feeling that the Stalker X-Bolt doesn't have the brass insert. If it doesn't, you will need at least a 150 grain head to stabilize it and get the forward of center correct. Slick Trick makes a new 175 grain crossbow head that might work too. The thing is ...you might have more money invested in testing all that...than you would if you just ordered what works. Hope this helps.