Take your time and find out exactly what it is your are buying before you spend a dime. Beyond simply wanting a sampler/MPC what other requirements do you have?
PreSonus AudioBox 44VSL | Sweetwater.com
*This interface has 4 mic inputs that have phantom power. Not there MANY more on the market. This one just came to mind due to it having 4 mic inputs.
You don't necessarility have to get an MPC if you don't already have one. You could look into a MPD pad or something like a Novation Impulse, Akai MPK, or M-Audio Axiom which will have keys and pads.