Not being familiar with the Magma, i am not sure what size you are looking for...I find something with around 60 liters (3500 +/- cu in) is pretty versatile, especially if it can be compressed for smaller loads. Something that size will carry plenty on gear intensive outings, and can serve capably on overnights and short backpacks.

The REI packs are quite good.They are pretty much bombproof, as is their guarantee.