While its not a "bad" setup, here are my recommendations for you.
1. The speedbag size is a bit big. You may want to go with a medium at the biggest. And if you're going to pay that amount from Everlast, you may as well pick up a pro gym speedbag like this one:
Speed Bag at Ringside.com
2.The Speedbag platform is functional, and includes a piece of crap s swivel , so its nice to see that you knew you needed to upgrade the swivel. However, I would recommend these for price and performance:
Standard Speed Bag Platform at Ringside.com That unit comes WITH a great swivel already, instant savings. Ive used it and the setup works well. It would be even better with the top of the line swivel, but that one performs well.
Make sure when you mount your platform to the wall that you mount two 2X4's to the wall vertically, and then attach the platform mounts to the 2X4's. It will provide a more secure mount, and better vibration damping since wood "gives" more than the wall surface.
3. As far as the heavy bag goes, the model you picked is decent, and is a good value. At the cost of $150 with shipping factored in, its a nice buy. But I would recommend this bag which in my opinion is better quality, PLUS its all REAL leather construction. It comes in at $185 with shipping factored in which is an even better value considering the all leather. It also comes with the heavy bag chain and swivel.
Leather Heavybag 100lb. Filled at Ringside.com
Your also a smart guy for reckognizing the need for a spring. I usually recommend a heavy duty spring to reduce shock on your chains/swivel and more importantly, the wall mount. It also helps to reduce the vibration through the mount as well. (keeps it quieter if for the rest of the house in a home gym application)
The one you have selected looks like an even better model than mine, and at the same price so definitely go with that one.
I wouldnt recommend the additional bag and swivel chain setup as its pretty long. Also, what comes with the bag you selected, OR the one i've suggested will be sufficient. It would be wasted money you could spend on a better swivel, handwraps or a round timer, etc.
QUESTION: How high is the ceiling where you will be putting the equipment? What build is the ceiling? (finished with drywall, open with wood studs, concrete, etc?)
I ask that because if its feasible to ceiling mount your bag, thats a much better option. You'll be able to work on footwork all around the bag instead of the back side being close to the wall. Heres a pic of how I mounted mine. I'd be more than happy to describe the materials and install process if its something you're able to do with your ceiling height requirements.
Keep in mind, that is a 150lb bag, and yours is much lighter so no worries there.
Overall, your certainly on the right track. Please feel free to ask any questions you may have and I'll do my best to continue helping you out.