One of my friend has the LOGITECH Z_5500 DIGITAL speaker system and it cost him around 20-21K [can't remember the exact amount].
I think that in order to buy a 500 watt RMS speakers u must increase ur budget. I maybe wrong.
See these model from SAMSUNG:
1>
http://www.samsung.com/in/products/h...er/ht_tp33.asp [500 watt RMS]
2>
http://www.samsung.com/in/products/h...r/ht_p1200.asp [800 watt RMS]
OR
U can go for the Creative Megaworks 550 THX costs around 19K. Don't know the current market price.