Syam, to give advice we need more info from you.
First of all 50k ???? of what US$? Euro? Rupees? Shillings?
Where are you and can you get easily to a good dealer with a wide selection?
I don't know much about Korg but am a Yamaha fan for many years so I would advice the PSR 710 - S910 or the latest S950. But you have also the A2000 and 610. All are excellent keyboards and it depends on your budget, how good player you are and what exactly you want to do with it. A church can be small from let's say 60 people up to (in South Korea) 6000.