Why not look into the Keystation 88es? It's not much more, but it's the cheapest thing with the full 88 keys in existence, which is definitely recommended because anything less is frustrating and limiting. The keys aren't entirely synth action, but they aren't weighted either. They have a bit of resistance and springiness to them, so it's possible to play with some expressiveness.

And yea you will need software to actually make noise with it, but the options are nearly limitless for that. I'm partial to Pianoteq myself.