600w or 400w for 2x4x7 tent. Flowering only

So my main question is will there be problems with the 600 hps. I'm pretty sure I can sufficiently vent the heat, its only like 5 bucks a month more, and I want to upgrade someday so I really have my heart set on the 600w. Is this way overkill or will I see benefits as well as problems.

If you plan on upgrading in the future I personally would go for the 600....Its more than likely u wont be able to sell your 400 for even half of what u got it for so it will almost be a waste...... so you might as well go for the 600 and just get a good enough blower.