Do speaker wires matter

@em2music:  I was not familiar with your speakers but looked them up — very nice gift someone made to you, especially if the drivers are in good shape!   With half the speakers rear-firing, it would seem that positioning out from the rear wall/corners would be important to the final sound.  And how nice to have such a large room to experiment with placement.  Have fun!

Thank you Bob540!:)

The Mirage M1s are an interesting speaker. Not only are they big and heavy, they are dipoles - they radiate both forward and backward. As a result, speaker placement is absolutely critical - they cannot be placed up against a wall with any expectation of sounding good. Gross sound quality for these guys will be more a placement issue than any other single factor.

You might want to read the Stereophile review here: 

https://www.stereophile.com/floorloudspeakers/689mirage/index.html 

Regarding your amp, let's set the amplifier myth to rest - a bigger amp will play louder, but not necessarily better. While the M1s aren't the most difficult load to drive, they aren't particularly easy, either. Marantz amps typically handle lower impedance load adequately, without triggering their current limiters that protect the amp but absolutely trash both the speakers and the sound. At 83dB/W/M per speaker, a pair adds 3 dB - 86dB, actually pretty loud. going to 2 watts, 89dB. add 10dB (10X the power - 2X10 =20W) for dynamic peaks in the music, 99db. So a 2226, while pretty low powered for these speakers, should push the M1s to reasonable levels. Disco loud, no. Living room loud, yes. A 100W/Ch amp would move the scale up 6dB, a 200W/Ch amp, 9dB. At normal listening levels, even a 2226B would be just cruising.  And while a bigger and better amp will sound, well, bigger and better, it's not going to have much impact on the sound quality issues ("The tweeters are not giving the detailed highs.") you are describing.

Speaker cable? Unless you are running 20 or 30 feet per speaker or more, 14 Gauge Clear vinyl zip cable is perfectly adequate from a power perspective, the power loss is insignificant.. You might be able to notice a minor improvement by spending hundreds of dollars, but only after other factors are attended to.

There is a final consideration. The Mirage M1 is more than capable of revealing shortcomings in your source material, most notably digital sources. After properly positioning your M1s away from room boundaries, consider the source. If you are listening to your average streaming from, say, Amazon, or God forbid, Sirius, the 'digititus' from low bit rate, repeated compression, encoding and decoding, would be quite apparent on speakers of this caliber. 

@chilli42, there is no difference in sound of a 3 foot pair of speaker cables to a 9 foot pair of the same cables.  If you think otherwise, it is a myth. 

@stereo5 , not true if your speakers are 6 feet away 😉

OP, you should try that other amp you have.  Its free and would take less than an hour to try.