Montecs that I used in the past were noisy that made a whistling sound. They were also tough to get really sharp. The closed design of the M3 should be much quieter and hopefully they will be sharper.
I started my daughter at 3 years old with a Mini Genesis and got 4 years out of it. Easy to resell (even a pink one). Then I got her an Infinite Edge (Bowtech) and at age 12 she now shoots an Eva Shockey. We have a great time shooting together.
I have a few McKenzie targets that seem to have accurate vital placement. they have replaceable cores and have held up very well. If you go to local 3D shoots, most clubs will have McKenzies or Rhinharts or a mix of the 2.
If you like how the Mathews feels and shoots, then I say go for it. As others have said, I would never buy a flagship bow with out shooting it first. Mathews has great resale value so if in a year or 2 you don't like it or get bored with it, you'll recoup a fair amount of your original...
For a hunting setup with broadheads I would cut them 1" in front of the rest at a minimum. At the front or slightly past the riser is a safer bet. For a target/3d setup 1/2" in front of the rest would be fine.
It would definitely be worth the upgrade to a newer, faster flagship bow. 22 fps is significant enough, but the draw cycle, less hand shock and increased quality would be enough for me to upgrade. The Elites just have a great back wall and generous valley that's great for hunting.
Are they cool...yes. Necessary...no.
QAD make a micro adjust non-dovetail version that is quite a bit cheaper. Even a Hamskea Hybrid Hunter with micro adjust is about $60 cheaper.