The 997 binder was the first one I got, and I've had a pretty good experience with it. The problems with it are mostly the problems with every binder I've ever heard of: it's a pain to get on sometimes, it's uncomfortably hot whenever it's warm, it's uncomfortable to wear for long periods of time, deep breathing can be hard, it wears out eventually, it can't make larger chests completely disappear. I wouldn't exactly say it helps me feel more comfortable, because it's basically an uncomfortable thing to wear. But it is effective enough for me on a daily basis (I have a medium sized chest, probably something like a B cup), and it also helps a lot with my hips. If you think it would be a good fit for you, and it sounds like you've done your research, then I'd recommend it.
I also had cold feet on getting my first binder that lasted at least four or five months, maybe over a year depending on how you count. I had the money, physically speaking, but I wasn't used to spending money on myself and I was still trying to figure out exactly what I wanted in terms of my gender. In terms of thinking through it financially, it sounds from other threads like you still live at home, so I don't know what you spend your money on, but you could try comparing it to other things that you might spend the money on. For example, I remember I thought about it in terms of the compression sports bras that I had been using to bind with--they were about $15 from Target, and that felt like a lot of money for me to spend at the time. But I wore them every single day, and in just two weeks that meant a dollar a day. A binder is twice as much as that, but I knew that if it helped as much as I thought it might, then it would be worth it to me soon. I also thought about it in terms of other ways I spent money (school supplies, deodorant and things, occasional clothes, gifts, hanging out with friends, fixing my bike, etc) until I convinced myself that a binder was at least as worth the money I was going to spend on it.
In terms of being ready in terms of your gender, I think that's a process that everyone moves through at their own pace and in their own way. If you're hesitating because you're not sure what you want, then it's fine to take your time and do some more thinking. Underworks is still going to be selling binders next month or next year if that's what you want then.