Also, I don't think you'd notice the difference too much if you had the chance to listen to the 2 boxes side by side (unless you have a trained ear for this kind of stuff). Don't go using insulation, theres the proper stuff and it can be bought from either your nearest car audio installer direct or some interior material suppliers. Its called Dacron. Its white and very fluffy. You can either line the box in it, or just stuff the box with it.
60L is a good size box, but just make sure its a good size for the space your going to place it in also.