I personally think reason is the way to go if you already have a capible computer. I think software has come along way where hardware, for the most part really hasn't made leaps and bounds. So i think reason is a great way to go. First, it's easy to use an external sequencer (and you can easily see what is where visually with no menus). Secondly, you don't have to worry about vst's which is a plus for me, cons for others.
However, if you use software, you are going to need some sort of a daw like cubase or protools to not only rewire software to (or render each track), as well as track your mpc to. So it may make more sence to start with a program like cubase. Since you have protools, you can try that, i personally hate it for what you are trying to do though. But if you have it, it's worth a try before you drop much money. Just see if you have any rtas sound plug ins or get the vst wrapper for it which will allow for vst's.
That said, i don't think another keyboard, or espeically a rack or two and a midi controller is the wrong way to go at all. Although i have not had any major problems with my computer setup, you can be pretty sure that your racks won't crash (or can you, seeing what happened to you, lol). But for the most part, you should expect more reliability, but at a bigger cost.
