We have several brand new builds for office PCs that are having problems due to poor regulation of the 3.3 V rail under low power conditions, and I am working to find the correct replacement PSU.  The systems have
MB: H270 chipset
CPU: i7-7700
GPU: None, integrated
RAM: HyperX Savage DDR4 16 GB (2x8GB)
SSD: Samsung 960 Pro NVMe 512 GB
 
The system draws ~22 W when idle (on but waiting for user input) and ~140 W under 100% full load (running variations of Prime95 and PassMark benchmarks).  The problem occurs at idle 22 W, the 3.3 V rail varies wildly and affects the NVMe SSD.  The PSU the system has now is of design where the switcher works primarily off the 12 V and 5 V rails, the 3.3 V rail is along for the ride.  So, if there is little to no load on the 12 V or 5 V, the switcher cuts back on the energy transfer from primary to secondary and the 3.3 V can then droop if under load as not enough power is coming from the switcher.  In this system, if we add a static load to the 12 V rail, it will work.
From what I've learned, I believe I'm looking for a topology with LLC converter on the primary side and DC-DC converters in the secondary on each of the raiils.
Obviously, the system's demand for power is low, so we don't need an enthusiast/gaming PSU.  Given this, which series of cost effective supplies would be most suitable, B3?
 

Pre-sales did not understand or was unable to address the inquiry with the information available to them.  In discussing application details, it was suggested that any of the 450 W and the 430 W supplies should meet my needs.  When trying to further explain the detail requirement for an independent 3.3 V rail supply, possibly with its own DC-DC converter, I was told "none of our supplies rails have DC-DC converter because our supplies run on AC and convert to DC, so our supplies are AC-DC."  It became apparent they did not have any useful information in assessing their product(s) against my inquiry.
 
I do know that many high-end PSUs have the desired circuit configuration, but it doesn't suit our application to buy such high-power, costly PSUs when all we need is less than a couple hundred watts.  We are simply looking for a basic supply with stable rails.
 
Corsair technical staff reviewed our requirements and confirmed their latest version of the CX series for 2017 (CX550, CX450, etc) has a DC-DC converter dedicated to the 3.3 V rail, and will properly support our usage.
 
On the web, I can find comparisions between this new CX series and EVGA's B3 series.  Specifically, Tom's Hardware has such an article, and also a news release from EVGA in April, with the release ending with "All new B3s use a modern platform, featuring an LLC converter on the primary side and DC-DC converters on the secondary side, for the generation of the minor rails."  Exactly what I'm looking for ... basic supply able to regulate under varying power distributions among the rails.
 
But, I cannot find confirmation of these statements anywhere on EVGA's website, spec sheets, or downloads ... or, even talking to sales staff!  Not going to risk it, going to look elsewhere.
 
Regarding the Tom's Hardware article referenced, PSUs 101, while good at reviewing details of the components and general principals, it does very little in discussing how PSUs operate, and as such doesn't discuss the different circuit configurations and their tradeoffs.  (I'd post alternative/additional websites but am unable to post urls yet)