There's no point on going aftermarket rods if you are only using OEM cast pistons.
Also theres no need for aftermarket rods if you arent really building it up for MAX power.

I just answered a question like this at G2iC.com
here's what I replied at that forum:

dont see the need for Aftermarket rods, for a basic all motor setup. Keep in mind that aftermarket rods may be even heavier than stock rods.
Unless you are making loads of NA power, the stock rods are good enough.

The only time we recommend Aftermarket rods, are:
1. going turbo setup
2. Building a high hp NA setup with aftermarket pistons