I am a new user looking into buying new speakers (M80i) which shows impedence of 4 ohms. I have Yamaha RXV-2400 which has impdence settings for either 6 or 8 ohms. Can I use M80i with my system or I have to opt for M60i speakers?

Welcome, Vipe. Don't worry about the 2400, it's a very powerful receiver which can handle 4 ohm speakers such as the M80s. Leave the setting at 8 ohms rather than 6 ohms so as not to limit the maximum voltage(and therefore power)which will be available.