Your better off comparing it to a amp that uses the same output tube compliment which has already been said. If you want to use the marantz's that you listed try those are more on par with the output power and tubes that they use.
Fairchild amps are a good example as as all of them used either 1614/(6l6gc) el34/6ca7 except the 275 but they didn't all start out using that tube compliment and changed it up from the 255 to 260.
When the Fairchild 255 came out it used a pair of 6l6 for tubes and power was rated at 25w. Then the 255a came out and the power increased to 30w using a pair of 6ca7's. The 260 originally used a pair of 1614 metal output tubes which are basically a 6l6 on steroids. The tube was mostly used in rf applications and allowed them to get the '50w claimed output. They then came out with a modification called the 260r revision which then allowed you to use 6ca7 /el34 tubes.