Just like yyzsantabarbara I have reviewed and owned the Coda # 8, # 16, and the 07x preamplifier. All terrific pieces at their price points. Unless you need the extra watts /current of the #16 to drive either very inefficient speakers or listen at insane dB levels the S5.5 will be plenty of amplifier for your system.
Their is no doubt in my mind that regarding the mid-range and high frequency range that, as of right now, the S5.5 has more pristine tonality, refinement in the micro-details, and one of the most beautiful presentations of the top end compared to the other Coda amps.. I would not call it "night and day" in its difference in these areas compared to the #16, but you can clearly hear it. Until, the System 150 amp ( which is a two chassis design and will retail for around $25,000) is released I believe the S5.5 is the most musical of all the Coda amplifiers and the least expensive! The only caveat is your speakers are not "pigs" to drive. So far I have tried the S5.5 with five very different speakers that it drove effortlessly and its sonic virtues shined through each time.
Teajay