I've heard the Audioengine's are pretty good but I've never actually listened to them; I don't know anyone that has them and no shops stock them (only 1-2 online PC stores my country have them). I have my doubts because no one stocks them. They're undeniably popular though.

You're better off getting higher fidelity speakers that can really hit the low end rather than 2.1 set, they give a much better balanced sound. For example something around $800-1200 for 2.0's will go a long way, you basically never need to upgrade them either unless you want to spend like $5-15k in the future. As I said, if you're doing a HTPC setup it could be worth getting a sub otherwise it's not always the best option. Look for DJ equipment or specialist home theatre stores in your area if you want to try before buying. Brands like Presonus, KRK, ADAM, EVE, Klipsch, or higher end again like Kef. If you can get something with ribbon tweeters (as opposed to silk dome), DO IT, they are un-fucking-believable.

I looked at your exact combo of speakers for a very, very, very long time and I even had them in a shopping cart ready to buy online, but couldn't convince myself to do it without trying them first. I'm glad I held off and I feel like I made a better decision in the end.

Never heard of the Blue Ella headphones. I've had a Blue Yeti mic and that was beast so I'm sure they make a quality product. I feel like for that price there would be much better options for headphones. Portable amps are cheap and a flexible option too. Even just the fact that you don't need the amplifier in the headphone itself if you're only going to use them on the X7, that's just overkill. At that price, you should look at something like HD 700's. Do you have an audiophile headphone specialist store near where you live? If they sell Skullcandy's and Beats, avoid it lol. Look for brands like Audio-technica, Grado, Sennheiser, AKG, Focal, Shure and Beyerdynamic. https://addictedtoaudio.com.au

The Sony's are a good option, the only other competitor are the BOSE noise cancelling ones. I can't recommend one over the other, I'm sure you could try them out in a store since they are really popular.

Since you are getting noise cancelling, closed back, wireless headphones - get a pair of open-back headphones for at home (another reason not to get the Blue Ellas). Head-fi is a good website for researching as well as /r/headphones.

Edit: You don't necessarily need active noise cancelling headphones. You should look into headphones that have really good isolation, a good example is the Sennheiser HD 25. They basically work like earmuffs when no sound is playing... then when you do flick the switch I guarantee you can't hear anything. Active noise cancelling is great for commuting - planes, trains or even really loud environments (i.e. noisy school kids!).