Marantz NR1200 with Emotiva BasX A-300

Hello @ajiayalur,  I see the Emotiva has a 12v trigger, but I do not see a trigger output on the Marantz.  Does it have one?  If so you need a 12v trigger wire connected. (usually a  mini phono plug, but needs to be specific for stereo or mono as required).  If not, the only way the Emotiva will turn on by itself is if it has current sensing and will do it automatically.  If this is the case, you may need music playing for it to sense the current and start by itself.  I have personally experienced this not always working (automatic current sensing turn on) on other equipment.

There is no trigger output in Marantz NR1200. How about connect this  https://www.ebay.com/itm/154311213185 directly to Emotiva input trigger ?

You can, but you still need to have something to trigger/turn on the power from that eBay power supply.  The key is still the power button on the Marantz.  If it is a hard on/off (i.e. if you turn the Marantz on and then disconnect the power, when you reconnect the power the Marantz comes back on) then you could us the "smart outlets" or plug the Marantz and the 12V wall wart into a power strip and use the on/off button on the power strip to control it.

To turn on the power to my Marantz and Emotiva, I use this power strip from Amazon.com: TrickleStar TS1104 7 Outlet APS, 1080 Joules, 3 ft Cord White : Electronics, which is controlled by my TV. When I turn the TV on or off, all the devices connected to the power strip will automatically turn on or off. However, the Emotiva still requires a manual press of the power button. My query is, if I connect a 12V DC 1Amp power adapter (like this one from eBay:https://www.ebay.com/itm/154311213185 ) to the Emotiva input trigger, will it power on automatically without requiring a manual press of the power button? Thanks

Yes.  The Emotiva should turn on with using the powerstrip configuration with the 12V power adapter.