Has anybody bought or heard a Chinese knock off amplifier?

The seller will service it. These are actual audio dealers in China, not just some guy selling stuff online. I bought a CD transport from the Queenway Store which was claimed to be a clone of a Wadia circuit. I broke an internal cable trying to open the chassis. I contacted the seller via the built-in AliExpress messaging system and they quickly responded and after a week or so they sent me a replacement cable for 1$. If you have to ship items back for service I believe the standard is that you have to pay the shipping, and they ship it back to you on their expense. At least one store I saw said they have a 30 day free shipping both ways in case of a defect.

Shipping from China can take a LONG time, and very expensive, especially if you have to use sea / train freight. Definitely something that should be considered.

Is this the same as a cloned Rolex?

Nothing wrong w a cloned Rolex as long as its doesn't say "Rolex" on it. Some folks are very happy w their Roleks watches. And I have no problem if the Chinese contract manufacturer make a "Roleks" amp at a fraction of the price of a "Rolex". If the manufacturing is farmed out overseas, why shouldn't the manufacturer get in on the action? A consumer can always buy the brand name version if that is important to them - there are considerable marketing & promotion budgets devoted to making consumers do that very thing.

Jungson (Zhongshen) is a spectacular sounding homegrown Chinese hifi brand that delivers some great class A amplification at very affordable prices. I have it in two of my secondary setups now. It is only getting beat by my reference Luxman gear that costs an arm and a leg.

I'm living in the Far East at present and wanted to try a valve amp, my room has a tiled floor and is lightly furnished, so thought this would be a good option. I ended up buying from ChinaHiFi previously mentioned in this thread and would say they are an excellent seller, good advice and help if needed, and pressed the button on this amp  RFTLYS A2 KT88 Tube integrated amplifier with headphone amp with Bluetooth input : China-hifi-Audio online store, and I have to say it is excellent for the money I paid, in fact I would say it would be good vfm for just the headphone amp that comes with it. Other Chinese amps that get good reviews and previously mentioned, Muzishare, Line Magnetic, Cayin  are now becoming well known names in the hifi community. When China is building these quality products why would their copies of well known amps not be good too? I did read on another forum, when purchasing some of these amps it is a good idea to budget for new capacitors which maybe not the best, although most of the reviews of clone amps I've read (there's not many of them) have been positive.