Hey Travis, sorry for being slow jumping into this one.
I presently ride an '03 EC250, but have time on the 200, 300 and 450.
The 300 is a smooth, grunty motor. Best ridden short shifted (unless modded). Sweet and easy to ride motor. Excellent for tight woods and doesn't tire you like many big bore 2 strokes or 250 MXers.
The 250 is still very smooth, but trades some of the low rpm grunt for longer revs. Glassy smooth, with no "hit". It definitely revs longer than the 300, but pays right off idle. For me, it's perfect. If I'm feeling lazy and not concerned about going fast, I can lug it and ride it like a small 4 stroke. If I feel like stepping it up, the thing rips!
The 450. Well, first don't let the weight scare you off when looking at the specs or lifting it off the stand. In the woods it feels very light and "flickable". Heavier than my 250, yes, but not a tremendous amount. Very comfortable and the weight is only really noticable when you have to lift it. Again, it's very smooth power delivery, with no "hit" (like the CRFs and YZFs). Deceptively fast really. Revs to the moon and seems to keep pulling no matter how high you scream it. Nice bottom end power too. Ridden back to back with a CRF it feels slow, but on the actual trail (and lap times), the difference seems to melt away. I'm told be several buddies with time on the KTM 450 that the overall power is nearly identical. The front end of the 450 is noticable more planted than the 2 strokes and feels like it EATS rock gardens for fun.
All that said, I still prefer my 250 to any of them. It's just the perfect compromise. Enough lugging ability to ride lazy, as long as your not in a hurry ;) , yet revs much quicker and smoother than the 300. The 450 is a great bike, but I still like the "quickness" of the 2 strokes, as well as the light weight ;)
With regards to forks. If you are a Pro rider, you will likely appreciate the additional performance of the Ohlins. However the Zokes are apparently 99% right out the box (compared to the Ohlins). I think if it were me, I'd put my extra money into a revalve of the Zoke (to your specs), as this is a bankable value regardless of which fork you decide on.