If you want it to be as close to a real piano feel as possible, you generally want hammer action. The cheapest keyboards with hammer action are the Keystation 88PRO (which I already showed you) or the CME UF8. The CME UF6/7 and Keystation 88ES do NOT have hammer action, they are just normal semi-weighted keys.

That said, they are cheap. I believe any semi-weighted Novation keyboard feels more like a real piano than a cheap hammer action one. Novation are generally said to be the best feeling keys in the business.

CME controllers are crap. They are cheap for a reason; the drivers suck balls (the device disconnects constantly) and havent been updated for years, the keys are stiff. The CME keys feel nothing like a real piano, and take serious effort to push down. The M-Audio Keystation 88PRO is quite ok though. The Keystation 88ES just feels a tiny bit better than a normal synth action keyboard.

Maybe you should go and try them all yourself?