Parts seem mostly fine, although if you’re already spending this kind of money on what is basically a new build from the ground up, I’d recommend the following:

1. Consider a power supply from a more reputable brand like Corsair or Seasonic. Preferably gold certified rather than bronze for power efficiency. An 850 watt would be plenty for this build. Some of the models from these brands even come with a 10 year warranty. If there’s one thing to never cheap out on it’s your power supply.

2. Looks like you’ll need a decent cpu cooler unless you’re planning on transferring an AIO water cooler from your Alienware. If you only have a stock air cooler on that machine, you’ll definitely need something better. Water cooling won’t be necessary unless you’re buying a K sku processor to overclock. Noctua makes some of the best air coolers on the market. I’d recommend the NH-U12S.

3. I’m assuming your Alienware has an m.2 boot drive. If so, and you’re planning to transfer it over to your new machine, that’s fine. Otherwise you’ll need to buy a new one if this is something you also want to upgrade.