Reply to Modular Setup options..on the cheap.

Hey everyone. I would like some suggestions for a modular setup. I have a hercules rmx and i hate it. I want to make a setup thats fun and stuff. I'll start with making add ons to what I have.
My eventual goal is to create a fun midi setup, for 4 decks, for cheap.
What I have:
>Hercules rmx

What I want to add on:
Traktor Pro 1: 99$
MPD 18: ~75$

are there better options for the money? I was believeing an x1, but i could probably get more pads and knobs for cheaper elsewhere.