OK friend here is the truth to your delima. Now I going to be doing some assuming here. Your arrows alone at 8.4 gr per inch plus fletching, nock and insert weight approximately 343 gr. With a 100 gr tip you have a 443 gr arrow and with a 125 gr tip arrow wt is 468. Now assuming your bow is shooting 275 fps (which is fast for the way you have it set up) with the 100 gr tip you will have 74.1 ftlb KE. Now you boost that up to the 125 gr tip (468 gr arrow) you will lose about 5 fps and your KE will be 76.3 ft lbs. So the difference is negligible both in speed and KE.
As for my Muzzys shooting right. All that was needed was a minor sight adjustment. But with the Slick Tricks - out of a tuned bow, no sight adjustment is necessary when switching from FTs to BHs. I do verify that prior to actual hunting of course.
My last comment is this - Its your money and if you want Muzzys so be it. I am just givng you my experience with what I've used. And I am sure you will find numerous members in here that will take the STs over Muzzys any day of the year.