I just got off chat support with them. They manually added the adaptor to my cart, and I was able to order it, discount and all! $28.55AUD all up. Weird that they didn't do it for you. I gave them the link http://www.amazon.com/Rock-Band-Legacy-Game-Controller-Adapter/dp/B01541ACLQ/ and they got it sorted no problems.

If they are the wireless ones then yes with a 360 Wireless adapter they work fine. If they are IONs or you use a Midi adapter you have to wait for the new Wired adapter from PDP to hit this fall. If you were a day 1 RB adopter and have a Wired RB1 drum set you're shit out of luck (like me!).

I don't think you need the Legacy Adapter you have in that list. ( Assuming you mean this ). Just Brain to midi pro to "This Thing" to XB1.
MS makes it kinda ridiculous to use legacy stuff on their new system.

Just used the chat support and he added the product into my cart so I could purchase it. I gave him the url http://www.amazon.com/Rock-Band-Legacy-Game-Controller-Adapter/dp/B01541ACLQ/ and he even added the promo code for me.. If your having trouble you could try this

I used their live chat support, told them I couldn't get to the link and they ended up adding the adaptor into my cart for me so I could purchase. When they asked for where I was trying to order it, I gave them this link: http://www.amazon.com/Rock-Band-Legacy-Game-Controller-Adapter/dp/B01541ACLQ/

Once it was in my cart I was able to apply the code and get the preorder in. Try that and see how you go!

Currently $15 for US customers

https://www.amazon.com/gp/product/B01541ACLQ/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1