Just looked at the back of those. Yes, Parts Express is decent but so is Amazon. Honestly found the PE connectors for whatever reason never keep a crimp well enough. I've thrown out many bags from them. You'll want to match the diameter of your wire AND you definitely want to use an insulated spade. The color on the insulation determines the size wire it is designed for. The insulation will minimize the chances of your amp shorting when you move a cable or the receiver.
Absolutely recommend a ratcheting crimp tool specifically for insulated connectors.
You may also consider a ring terminal instead of a spade in this case, if the screws come all the way out.
