watts or joules?

I have a pair of martin logan aerius speakers,the local dealer here told me a long time ago when I know that I need a lot of power he recommended ARvt-50,but I said it's only 50watt? He said yes but its high current and that is what I need that amp has some 360 joules of power Ihave heard AR's ca-50 same 50 watts but only 160 some joules and it souuded very weak,Some amp companies don't even know or underwtand about joules,an old carver amp used to measured in joules only.As of my knowing only Audio Research,and Carver list joules of power,Why? Any insight to this ?Thanks Nick