Sask, welcome. You haven't indicated what features are most important to you, and that's what should determine your decision. The three units that you mention differ only slightly in maximum power capability and this shouldn't be of significance in real-world use; all have plenty of capacity. They will be transparent, without any "sound" of their own(the third post, which appears to be intentionally antagonistic, has no factual basis and shouldn't be taken seriously).
Among the features, note that the 5600 also has variable(80,120,150 Hz)crossover which some previous models didn't have. However, it lacks an auto-calibration feature which makes things simpler and is possibly more accurate than a manual calibration would be. This would suggest preferring either the 2805 or the 3805. Note that the 2805 includes the microphone, generally about $50 extra with the 3805.
