Marantz has been making amps since 1953, one would guess they've figured it out buy now.
But many factors matter.
How much do you have to spends?
What are your priorities?
Do you favor power over quality?
Marantz are good amps ... in their price range. Though if you check the full line, Marantz covers from Hundreds to Thousands per amp. You get what you pay for.
Next - Stereo Power Amps or Home Theater Power Amps?
Stereo Power Amps tend to be Class-A/B, where are Home Theater Power Amps tend to be Class-D or Digital Amps. For pure music, I prefer Class-A/B amps; simply for efficiency, many people prefer Class-D Digital Amps for Home Theater.
Unless I am mistaken, the Parasound multi-channel Home Theater amps are all modular Class-A/B. They consume more power and generate more heat, but many feel they sound better. Opinion ... everybody's got them.
Rather than ask a question in isolation, how about some perspective.
How will the amp be use?
What will the amp be used with?
What are the dimension of the Room the system will be in?
How much money do you have to spend?
Are you going Pre-Amp/Processor/Power-Amps or is it better to go AVR?
Assuming a person can afford it, Parasound makes a 3-channel Power Amp (250w/ch), You could combine a 2-channel Parasound Amp on the Front channels, then the 3-channel on the Surround and Center for a 5.1 system.
Or as an alternative, a 2-channel on the Front, and a 5-channel on the Center and Side/Rear Surrounds for a 7.1 channel system.
You can also mix-and-match. I don't seem much value in Parasound's AV Pre-amp as it seems all Pre-Amp and no Processor. So, I could see a Marantz Pre-Amp/Processor on the Front end and Parasound Power amps on the back end.
Marantz does make a 2-channel Power Amp (140w/ch, MM7025) and they make a 5-channel (MM7055, 140w/ch), and a 7-channel (MM8077, 150w/ch). So, in this case, I might have the 2-channel 7025 on my front channels and the 7055 covering the rest in a 7-channel system.
Though, if I had the money, I would prefer the 250w/ch Parasound Amps. (A21 =2-channel, A31=3-channel, and A51= 5-channel)
Budget, preferences, and circumstance really carry very strong weight in making your choice; far more than this brand vs that brand.
But to the core question, Yes, Marantz amps are good, and have consistently been in business making good equipment since 1953, while many other big name brands have fallen by the wayside. They didn't endure by making crap.