I'm also curious to learn the internal differences between the 400w & 460w. The following makes clear what my guess would be if I were to make one.
I'm of the opinion that there isn't a sufficient market for both the 400w and 460w, particularly given the current price difference (around $20-30 at the moment). The 60w differential is unlikely to support the price difference because anyone pushing 400w, let alone filling that small gap between 400 & 460w, is likely to error on the side of caution and purchase a fan-based PSU with a higher output rating. Besides, the overload tests [url]=http://www.hardwaresecrets.com/article/Seasonic-X-400-Fanless-Power-Supply-Review/1073/8]conducted by Hardware Secrets[/url] indicates the 400w will perfectly serve the market of people needing 460w (of course, that test isn't definitive and doesn't take into potential long term consequences).
Perhaps recognizing this, Seasonic neutered the 400w package by including only a single PCI-E cable (being the 2nd of only 2 differences between the products). It's hard to imagine a common setup which draws close to 250, let alone 400w, without a video card that uses 2 PCI-E cables so the exclusion of a 2nd PCI-E cable is clearly marketing related. This is further confirmed by the present marketing
of the 460w: "Coming with two PCI-E connectors, the SeaSonic X series SS-460FL Active PFC F3 allows you to build up a SLI or CrossFire gaming system." Most SLI or Crossfire setups appropriate for a 460w would also work within the confines of 400w. Again, that 60w gap simply does not open up a whole new set of configurations. There is no justification for including 2 cables with the 460w and only 1 with the 400 except for marketing purposes. The Seasonic reps failure to affirmatively address
the issue further suggests this (2nd post from the top). While it may be true that most 400w units don't have dual PCI-E plugs, most 400w units are not priced at these levels and a 2nd $.50 PCI-E cable would not have altered the economics of this item.
Ultimately, marketing alone will be insufficient to maintain both the 400w & 460w given the size of the market. Most users purchasing this unit will simply opt for the cheaper unit and use a 2xmolex to PCI-E adapter if necessary. They'll be happy with a great PSU but leave some goodwill behind for feeling nickel and dimed. Consequently, the price differential will shrink between the lines removing any incentive of Seasonic & retailers to offer both units. If Seasonic develops a 500w fanless unit, they'll drop the 460w unit. If not, we'll have the 460w unit. Perhaps OEM's will find sufficient value in the difference in order to sustain both units but it's unlikely.
That being said, thanks Mike, Newegg &/or Seasonic for the promo discount. A discount is a discount for those who must buy the 460w right this moment (there's no retail price competition at this time b/c so few have the units....we'll inevitably see a drop in prices of both units as well as a decreasing price differential b/w the 460 and 400). And, thank you Seasonic for what appears to be a great PSU and filling the void of a relatively niche market. Alas, can't you just sell us a PCI-E cable for $5?
Search terms: SS-400fl x-400 x-460 x400 x460 ss-460fl PCIE video card