If you're still living in Illinois when you go to buy this kit, you may want to check with your state's DMV. The last thread I read on state laws included a reference by someone in Illinois that all e-bikes are classified as mopeds and must be licensed and insured. Also, there was a speed limit on mopeds in Illinois, which may still be applicable--30 MPH is the upper limit for mopeds.
People mistakenly think that because there's a reference to electric bike standards in federal law that it some how compels states to allow electric bicycles to be operated on public roads. That's not the case, Congress has left it to the individual states to determine whether electric bicycles can be operated on their public roads and what conditions to impose if they are allowed to be operated on the roads. The federal law only sets safety standards for finished electric bicycles sold in the US. Laxer federal safety standards that are set by the Consumer Protection Safety Administration only apply to electric bikes with speeds under 20MPH and motors 750W or below. Electric bikes that don't meet those standards (they're faster and/or motors are more powerful) must meet more stringent moped/motorcycle safety standards set by the Federal Highway Safety Transportation Administration. That's why you don't see many production bikes with specs similar to these 1000W Chinese kits. Ultimately, I expect Customs to start cracking down on the import of the more powerful kits into the US.
I'm glad you're looking at bikes with disc brakes. I also wouldn't put it on an aluminum frame. I'd want a beefier steel frame. You should also wear the appropriate safety gear if you're planning on riding at motorcycle speeds.