Do you mean 50m3 or 50m2 ?? if you mean 50m3 then your room is about 20-25 square meters (m2) depending on your ceiling height. Its a big difference of 20 or 50 square meters :-)
You should take a listen to Dynaudio AIR20 or AIR25. Great speakers...
http://www.dynaudioacoustics.com/Default.asp?Id=534
If your room is 50m2 then you should do yourself a favor and listen to B&W 801/802 Nautilus, together with a great amplifier. The same that Abbey Road use, among others. They need a good room but when you get that sound, they sound fantastic great! Should be able to find a used pair for about 5-6000€ and the rest goes for a good amplifier. Check out Bruce Swediens choise, the Danish company "Electrocompaniet" AW180 (monoblocks).
http://www.bwspeakers.com/index.cfm/...20800%20Series http://www.electrocompaniet.com/prod...amp/aw180.html
Remember that your room decide if it will sound good or GREAT
Good luck!
/Majk