If they are 2 ohm (and that is what the orignal speakers were) or numerically higher, you will be fine. What your friend is talking about is some systems use a 4 ohm speaker, and if you install a 2 ohm speaker in its place, you could damage the amp. What happens is by installing a lower ohm speaker, you "force" the amp to deliver more power than what its designed to do, therefore damaging it. You should be able to take your speaker to any autosound store and they can check it for you. If you have a volt/ohm meter handy, I can walk you through doing it yourself. Hope that helps...
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