I have the BX5a and they are quite nice -- they sound good and are solidly built. Even though they are certainly smaller than 8 inch bookshelves, they are quite a bit larger than your typical computer speaker. They also have some substantial weight. Now, I'm sure the dimensions and weight are posted somewhere online -- definitely consider these aspects.
The Swans M200 cost considerably less, and they don't nearly have all the 'features' of the bx5a that would tend to make it in the same class sonically. For instance, each bx5a speaker has a dedicated built in amp, is bi-amped, and so on. These things don't guarantee better sound quality, but they certainly help.
The other thing is you probably would want to consider speaker placement -- which is quite important. I don't think putting the speakers right on top of the desk is optimal. Ideally, they should be raised to about head level and not have any obstructions that might block their sound.