[The CP-850] is completely unmatched by any ATX unit on the market I can think of. You'd have to spend twice as much as this thing costs to find the next best thing, performance wise. I'd like to see some better capacitors in there, but you just can't fault the CP-850's performance here.
I don't know how Antec managed something this awesome for such a low price, but they must really want the CPX form factor taking off if this is the performance we're getting.
The Antec CP-850 is a superlative power supply by almost any standard. Its electrical performance is up at the level of its more expensive brethren, the Signature 650 and 850, and Seasonic's flagship, the M12D-850: Voltage regulation is extremely tight for all the lines at all loads, and the ripple noise is amazingly low.
The noise performance is excellent, with the <400W performance matching or bettering virtually every PSU tested thus far. Above 500W load in our heat box, the noise level goes over 40 dBA@1m, or about the norm for PSUs rated this high. It has the virtue keeping itself extremely cool, however, cooler than any other PSU we've tested at such high loads.
A serious consideration is that in each of the three compatible Antec cases, the CP-850 mounts on the bottom, and the intake for the PSU is quite separate from the rest of the system....The above is an obviously unfair advantage for the CP-850... but what of it? Antec has used an integrated systems approach for its CP-850 and its best cases, and if that approach is an advantage over all other case/PSU combinations, then, all the more power to Antec!
For the quiet-seeking computer gaming enthusiast, the CP-850 (along with any of the three compatible cases) is something of a godsend. Fantastically stable power, super low noise at any power load, long expected reliability due to excellent cooling, modular cabling, and all at a price that's no higher than many high end 6~700W models. That you're limited to one of three well-executed high cases from Antec — one mostly for silence (P183), one mostly for gaming (1200) and one that's really an ultimate everyman case (P193) — is not exactly a hardship either.
The CP-850 is non-standard, but compelling, and in its typical application, as powerful and quiet a PSU as anyone will ever need.