I agree with Kuki. Expedia rarely gives you the best deal. Other agencies can often beat them. Do check around and see if there are better deals out there.
I will add that on one cruise I took in 2003 a "mega" online agency had the best deal but, since then, they have not been able to beat other agencies.
One other thing to keep in mind is that any agency can sell you a cruise but they EARN their money if and when something goes wrong. This doesn't happen very often but when it does you want someone on your side who WORKS, for you, to make things right.