Of the three hertz you mentioned - MPX 165.3 The HCX and ECX aren't bad speakers, but the MPX are simply better and worth the extra coin. If you're new to hertz you need to know that they are one of the most bootlegged speakers on the market. Make sure you are buying from a reputable source.
Did I see in another thread that you may be paralleling the 2180 to 4 speakers? If so, keep in mind that means you will only be getting about 120W to each speaker. Hertz speakers like power and they would be fine with 180W going to them, but 120W is leaving a lot on the table and you may not be happy.
Not to muddy the waters, but I'll also throw out the option of the WDX6MOTO. A lot of guys on the other forum are going to them and seem very happy with them. I have not used or heard them so can't say one way or the other. Some of the guys over there run through speakers like most of us go through toilet paper, so the fact that they've been around for a few months and guys are still recommending them is a good sign.
Freedom isn't free, remember to thank a vet.
2018 CVO RG lava orange, 117 Stage 3, 14" F47 and a few chrome extras. Boom crap gone.
2016 RG Special Cosmic Blue, 120ST with Dragos 2:1 and TTS tuner, FBI drop seat kit and JNR air ride. Stock audio long gone.