I don't think the general ergos are an issue on my alto, but the left hand pinky takes a little getting used to. I understand pitch is normally the main issue with many Sopranos. Would I be better off cheaper modern horn?I personally am not really bothered by the ergos of older Conns (I play a Chu tenor) but it depends on you - what you're switching from and how much you are bothered by changing ergos.
As far as sound, I think Chu sopranos (which is really a misnomer since Chu berry was a tenor player haha) sound really fantastic. The have a round, warm sound that is quite different from modern horns such as selmers or yamahas. The catch is that if you aren't used to them, pitch can be squirrelly. They won't lock in for you, you have to be paying attention. This is just based on my own experience and I play with a "jazz"-type setup so it could well be different for you.
As always, try it out for yourself. $600 seems like decent price to me if it really has been recently overhauled.
My other question, which I forgot to mention in my original post. I'll soon be a music major. Would a soprano be something I'd need to invest in anyway for Quartets and such? And if so... Would this last me?