make sure you dont just get ANY carbon arrow. they vary widely in GPA(grains per inch) and can make a huge difference in speed and power. I personally shoot 60lbs and im dropping down to an 85 grain head and the carbon express maxima arrow. I know i can pick up a lot more speed. The lower price carbon is heavy. You tack a 100grain broadhead on a 28" arrow at 9.9 grains per inch and youre shooting buffalo material. You dont need that on whitetails.
Ive tried almost every broadhead there is too try and I keep coming back to the American Broadhead Company Sonics. They fly great(zero plane technology), are sharp AND REASONABLY priced. You get 6 for the price of other companies three. I just havent found a better flyer or penetrater for the money. Youll hear a variety of opinions but Im telling you, ive done them all... rage, slick tricks, muzzy, magnus and when i order my next set of sonics im ordering 3 packs so that if for some unforeseen reason they quit making them I can shoot them for a long time to come.
http://www.americanbroadhead.com/
oh and FYI, based on what ive seen Carbon Express makes the lightest GPA arrow on the market. You really need to calculate this out and see what you NEED. Not what everyone else is shooting or your down range trajectory will really suffer.
Most people shoot 100 grain or 125 grain because they think of it like bullets. Broadheads and bullets are not the same. A heavier head gives better penetration on bigger game and thats about all there is too it. A broadhead thats 85 grains USUALLY is the same or very close to the same cutting diameter. In fact, the sonic 85 grain is a 1" cut while the 100 grain is only 7/8" cut.
PM me if you need any help.