I'd also check out the
Presonus line of products.
Your drum kit will need a MIDI I/O and your keyboard could use the same interface or use the USB cable direct to the computer. Your mic will need an input and I'd suggest making sure there's phantom power available in case you move beyond dynamic mics. Also, don't underestimate the impact that the mic preamps have on the quality of the recording. Check device reviews on this point specifically.
I'd get a device with as many I/O options as your budget will allow. Too many options is a better problem than too few. What you're looking for should be easily accomplished with your $500 limit.