Having heard them side by side for a bit, I'd pass.
IME, the O300 are a lot better than the 400. The 400 is an older design in their line, perhaps being phased out or readied for replacement because they're a bit superfluous to the 300s.
In the grand scheme of things, you could probably do much worse than the 400, but the comparison is not likely to favor them.
-dave