Just get them balanced if you plan on running 600 or less rwhp. You just get them balanced is all that you need to do. Weight only matters to make things rev more smoother and to get a higher rev limit. So you really need to worry about balancing the whole motor assembly to get the most of everything. Going with aftermarket rods Just affords better revving, and higher rwhp reliability due to high tensile strength, and that is what you are really looking for.
I want to know this too, and specifically how much lighter than the standard rod is the eagle rod? Any other brands to go for? I heard the eagle rod for a 2JZ is half the weight of the stock rod,is this applicable for the 7M also?