Yea, honestly, having three PCI ports seemed a bit much to me. I mean, there are still tons of PCI devices, but it seems kinda rare that someone would need more than one or two of them nowadays. An extra PCI-E port would have been better, and I debated whether or not I should mention it, but it didn't seem like a bad enough issue to warrant mentioning in the article.
Really weird, the whole I/O section is a master-class in wasting space; the VGA and DVI ports should be swapped for a Displayport (or mini version), which frees up more space for audio ports. I'm also endlessly bewildered by the insistence in including a PS/2 port; how many people actually still need one of these and don't already have a half dozen USB to PS/2 adapters? I'd have moved the USB + Ethernet to that end, and swapped the other USB ports for one of the combined four or six port blocks.
This would free up a ton of space for extra audio connectors, while still leaving plenty of room to separate them if you absolutely have to do-so.
I agree with most of the previous comments but I would add that this was a missed opportunity for a motherboard truly customized for the HiFi audio, DIY market. There has been a lot of interest in high end, computer audio for several years. The Z170Z5's mediocre on-board audio isn't a problem for this market because the preferred solution has become the USB port, and literally dozens of asynchronous USB DACs with internal, high quality clocks are available in price ranges from $100 to over $10,000. What is needed on a retail MB to take advantage of these high quality DACs are enhancements like those being built into dedicated music PCs, which I think are generally very overpriced, inflexible and typically not up-gradable. These would include better shielding of the USB port from RF noise inside the PC, ultra low noise regulator and 2nd stage filter for the USB signal, separate, highly filtered USB power supply, along with an on-off switch for self-powered DACs, etc., etc. Also there should be over current protection and ESD protection for the expensive equipment that will be attached to the USB port.
PS. I don't care if someone here doesn't believe that they or anyone else can hear the difference between an on-board DAC and a $10,000 piece of high end audio jewellery. My point is there is a potential market niche that is not being supplied. The external DAC market segment is one of the fastest growing in high end audio, and a well designed HiFi motherboard could potentially sell in this market at a significantly higher profit margin than commodity motherboards.