Their lower end units, which the 630W unit is, is a pile of crap. They make a few good units for the upper end, but then if you were going for the upper end, you wouldn't be looking at AXP, because there are excellent units up there, not just "good"
Wattage means very little, the modxstreams don't stay within ATX spec for ripple at high loads, while the seasonics do...and they do it brilliantly at that, the S12II is by far the best ~500-600W unit available on the market at this point in time. I would stay far away from AXP. The Seasonic is rated for only 24 watts different than the "600W" OCZ unit on the 12v rails, which is a mere 2 amps.
And NO OCZ units have ever been made by CWT, the Modxstreams are made by Sirtec, the StealthXStreams are made by FSP, and the GameXStreams are made by FSP. Some of the older units were made by 3Y and Topower.
I wouldn't know, that is why I said going by the prices on the egg. Your location says US/swe, and unfortunately, I don't know any swedish sites.
And why do you "need" 600W? Unless you are running dual video cards, overclocking and have lots of drives, there is no need for it. Besides, watts aren't everything, the seaswonic unit will put out power much much better than either of the units you put, even though it is rated at 80W less than the others