Allek - Welcome! As you'll notice, there's a spectrum of opinion on the arrow weight question. At the end of the day, lots of different things may work, but you'll have to draw your own conclusions about what works best for
you and the species you hunt.
As has been said here many times before - yes, lots of animals have been killed with 125 gr. heads, but that doesn't mean that it isn't possible to do better. Just because it's "traditional" doesn't mean that there still aren't ways we can potentially continue to explore and improve. With all due respect to Mr. Bear, I'm not going to let what he did define what I choose to do, and I don't think he would have wanted it any other way. Tradition isn't the worship of ashes...
Increasing FOC and general arrow weight doesn't just provide improved performance on really big game, though this is a common misconception (as is the suggestion that those who advocate for higher arrow weight don't still prioritize good arrow placement). It can help any time that a shot is less than perfect, hits bone, etc. Of course we all want to strive for perfect arrow placement, but there are a lot of variables with any shot, and, as with many other things in the real world, what we strive for and what actually happens doesn't always conveniently coincide. Even Howard Hill and Fred Bear made bad shots now and then.
Keep in mind that, with comparisons to what "Fred Bear used to shoot," that he was also often shooting a #65 bow, and Hill was often shooting significant higher than that. Yes, they may have shot lighter heads, but with heavy bows. Properly increasing your arrow weight and FOC can allow for the same effectiveness (or even better) with a lighter draw weight, and why pull more than you need to?
In my opinion, speed isn't a replacement for momentum, just one part of the equation. I think that even a lot of compound shooters with the fastest bows on the market would still do well to pay attention to more than just outright speed.
For a good explanation of the benefits of increasing FOC, check this out:
http://www.alaskabowhunting.com/Three-Darts-W13.aspx And this:
http://www.alaskabowhunting.com/Ashby-On-Momentum-Kinetic-Energy-Arrow-Penetration-W19.aspx