Although you can get a 7.1 for 50k, it is not worth it to spend 50k on such a cheap 7.1 when you can get a better quality 5.1 for the same price.
To truly experience the power of 7.1, you will need to spend lacs on your setup, and then too the difference won't be much except in huge rooms, if at all.
I would suggest get the best 5.1 you can afford.