I am currently an intermediate level piano player and am looking to purchase a new keyboard. I started playing on a Casio Ctk-4200 which is a entry level piano with 61 keys. It was perfect to learn the fundamentals but now I feel like I need more keys as well as better sounds. At this point I would like to spend less than $1000 on a solid keyboard. I am looking to keep it long term so I want to make the correct choice. Ive been looking at the Yamaha MX88 as well as the Korg Kross but they both look quite old and am unsure if I should consider them. Ive heard that 88 weighted keys are essential. I also need it to be reasonably portable I am open to buying used keyboards if it is worth it. Thanks!