I've got an answer. There is no such beast.
I've you've been keeping track of the messages here on the forum, you've seen that the variety of DC-DC solutions are definitely now increasing, in part due to the success of ITX, but the prices are still high.
There is no such "best" PSU, it will really depend on your particular situation and desires/needs.
Opus is a great unit, yes, if you want a turnkey PSU and don't care how much you pay, then Opus or Keypower seem to be your best choices.
If you're on a budget or just like tinkering and have time, you can build your own PSU for relatively cheap ($30-$50) to whatever specs you need.
If you're trying to power a P4/3.0 (82W max), then you're gonna need a beefin PSU, however if you're gonna power a P3/500 underclocked to 333 (20W max) then a base sproggy will do you fine.
So to answer your question, there is no simple answer. It all depends on the factors involved. For example:
a) What is your total system power?
a.1) What type of CPU are you powering?
a.2) How many peripherals are in your system?
a.3) Do you have any other devices drawing current off your PSU? (GPS/USB devices/etc)
b) What is your budget?
c) What is your level of electronics expertese? Can you operate a soldering iron?
d) How soon do you need it?
e) What physical size must the PSU be?
f) What do you currently have?
There are many different options available. If you already have a computer that has a 12V PSU (Cupid, Epia, BookPC, etc) then you could just add on a regulator for the 12V output, and run the rest directly off your computer. The possibilities are endless.
The most popular however is to use the Opus, it looks like.
Because in order to make it a worthwhile business venture, creating a PSU with the capabilities of the Opus would cost almost as much as the Opus does. That pretty much goes for "why isn't there a clone of the XYZ PSU out there" question as well, in order to make a worthwhile business venture, it'd cost too much.Why hasn't somebody made a unit the same as the Opus and sell them thru here?
There are people like Jeff Mucha who has a "commercial" PSU that he made and sells, 70W for $150, however with the prices coming down on other options that isn't such a good price anymore. Maestro just puts together the public-domain Sproggy design (60W) and sells it (completely assembled for $150). The cost of buying all of the components is probably close to $60, so if you add in time to assemble, test, etc and a bit of profit you're looking at at least $100, and it looks like there are several new PSU options that are coming out for < $100. People are also interested in warranty and knowing that their unit was "professionally created", which you can't offer in a "garage company" operation.
As your question stands, sure, get a KeyPower 250W ATX power supply. However you forgot to mention price, which is ultimately the deciding factor. If you don't have $250 to blow on a DC-DC PSU, then it's not an easy question to answer.realize there are different needs for different users, but really, if there is 1 ps that has all power rails (even if not needed), decent wattage and the above options, wouldn't just 1 dc-dc ps be good for all?
If you are looking for a cheap professional PSU, we're organizing a group buy for the MagicPower MPD-810H (120W) (comes with cables, turnkey solution) which looks like it'll be around $100USD landed in your lap. Feel free to join
Arise also offers a good deal, about $120 for the same unit on a per-customer basis. They don't believe in bulk deals though (they offer $2 off per unit for > 10 units, and won't even ship to individual addresses).