In my opinion, You should put the big money in the front, since that is where the majority of the dialogue in movies, and most of the effects occur. The sides and rear, from my observation provide the ambience which may be nothing more than a leaf rattling in the breeze, but could on occasion include a jet flyby. In either case, the frequencies are in the upper range, where even the M33 would be sufficient for the surrounds.

On surround music, you MIGHT find that this does not always hold true. A good recording mix will balance the sound relatively equally around the room's speakers.

The range of the speaker may not be a serious issue if you are using a good quality sub, since the LFE will be processed out to the sub. In that case, the 5000's would probably be a good choice.

If you plan to use the system mostly for music, go for a better set of surround speakers.

If you are going to use it for video exclusively, you may be perfectly happy with the 5000's in the surround locations.

One thing that I didn't see in your statment above, was the size of the room. This aspect of the equation will play a significant role in the speaker choice.