I've heard bad things about Cooler Master Power supplies over time. They're better than oem psu in prebuilt pc's though. It would handle one r7 260x but I wouldn't crossfire on it till you get a better psu, it's not worth blowing out the PSU and frying everything with it....I know I'd be very sad if that happened to mine lol. I wouldn't crossfire on your current cooler master psu.
edit: oh, and yes the EVGA one is a good power supply and would handle crossfire, the corsair builder is usually even cheaper and it's recommended and has good reviews from johnnyguru the trusted PSU review site