RMS power ratings really have nothing to do with what power you are seeing during normal listening. They are created using testing procedures that are like night and day when compared to popping in a CD and playing some music. Music rises and falls in volume and changes in frequency. Sometimes you are seeing a few of those watts. Occasionally when you reach a 'peak' you may see all 26 of them for a brief instant a few times per song. Even with a separate amplifier making decent power, say 100 watts/channel, at any given time you may be seeing about 15-20 of those watts. At other times, 50 or 60. For brief instances you may see that 100 watts. In both cases it's quite possible that 100% of that wattage may never, ever actually be delivered if you never get anywhere near max volume. An amplifier isn't just beneficial due to a higher rms power rating but also because it delivers more clean power and better sound during normal listening than your head unit will. At times when your head unit is only giving you a few 'watts' your amp may be giving you 4-5 times that amount.
Really matching RMS ratings is of little use except for deciding exactly how much loudness you're looking for because you have to be able to deliver a certain amount of clean power at your normal listening levels in order to get a sufficient loudness to be able to appreciate the details in the music. It takes a doubling of power to get a 3db increase in loudness which has been determined to be the bare minimum that is perceptive to the human ear. Nobody thinks everyone who wants decent sound has to have amps and spend lots of money, but it's considered a waste to get good components and then limit their potential.
You may not have received lots of replies or advice to your other thread because others are tired of trying to convince people that they will be unhappy with such a setup and have decided that it's best to let people spend the money and find out for themselves. You may actually find that what you want to do will satisfy you but if you end up driving around with the head unit volume at 32 out of 35 90% of the time then you know you need an amp. There may or may not be components out there that will sound OK off of 26 watts, the issue being that most manufacturers find it easier to design an excellent component set that requires power than an excellent component set that requires very little. IF you want to give it a shot look for something with an rms rating of 50 or 60 watts and a high efficiency rating, like over 90db. I just think there is only so far you can go trying to make improvements off head unit power before you face diminishing returns.
And BTW I know a friend who used to compete using a separate amp on high end components in a Miata and I don't think there was a huge amount of custom work involved. IF you ever considered changing your mind I would ask him where he put his amp and relay that to you.