Blackbeard
I'd be interested to know if there's support for this (i.e. a low wattage Platinum unit, with or without the DSP).
I can't speak for everyone, but I think it would be worth looking into. I can't imagine the ‘modest desktop/gamer’ market to be small by any means. And certainly there's no shortage of people looking for high efficiency units for low powered boxes to power their ITX rigs, servers, HTPCs, etc. I'd humbly leave it to your market research bods to figure out how warmly it'd be received. ;)
Blackbeard
The benefits of the extra efficiency would diminish at lower loads, or is it simply a case of wanting the performance/features, efficiency aside?
A bit of both, but less of the former and more of the latter. I mean most machines realistically really don't draw more than ~300W. I've never had more than 1 mid-high-range GPU and really not interested in overclocking, haven't been since the Core 2 Duo days. But I would be interested in a high quality, high efficiency, clean power PSU. It doesn't really make any sense for me to splash out £175 for a 860W when I don't use half that at full load with CPU and GPU burners, stacked out with drives etc, and likely wont unless I win the lottery or something and go a little nutty with a silly high-end SLi rig. So for me at least it's a value/utility proposition thing, and a ~£75/~450W unit would make a heap of sense.
But I really like the look of the AX series, you've turned out another fantastic PSU series. Bravo.