Well, we need to evaluate how much are you going to use this saw with a 24"? How much to you realisticly want to spend? Do you see a need in the future for wanting/needing a bigger saw?
Here's the thing, I stated out with a 350 as well, still love it, if I had to have just one saw, that would be it. I wanted something bigger, I boutgh an MS390, it was an OK saw, but the first tree I felled after buying it, It was too small. I needed at least a 28" bar for it, that wasn't going to happen in Oak. I hired a guy with an 046 to stump it for me. It was a fine saw otherwise though.
I found a used 262xp at a garage sale. It was lighter, had more power, and cut circles around the 390. I sold the 390, and bought an 046. It uses more gas, but cuts twice the wood in half the time, it has been an ideal saw for my needs, and I find I use it more than I really need to, just because it's so fast!!
When we speak of buying up, it's because we have been there. You buy the saw you think you need, then want bigger after a while! Had I bought the MS440 I wanted to the time I bought the 390, I would still be fat dumb and happy! But I chose to save a buck, I ended up spending several hundred more in the long run.
Just some food for thought.