CdotS:
Listen to the one line arunmrao states: "Watch out for availability of service, spares." The steel mini-mill where I used to work is a good example. They had an older ARL unit which required a lot of TLC. Then, due to the state of the electronics, finally had to be retrofitted due to the lack of spare parts. Retrofitting can be expensive and in some cases not possible. Also, you said you found some used in a foundry. Depending on their location and the environment they operated in, there may be some serious concern. (The internals may be seriously damaged by vibration and/or dust particles.) So my advice in the arena of used equipment is BE VERY CAREFUL.
One more thing, concerning used spectrometers. There should be a maintenance history on them. With my last two companies, we had yearly (once or twice a year) major maintenance (cleaning, realignment, PM, etc.) performed on them by the manufacturer's representative. If I were seriously considering buying a used machine, I would try and track down the maintenance history on that machine.
Also, you are correct about the addition of other elements to your analysis. However, if you are buying a new machine, it is better to get everything you need up front (cost effective). The last arc sparc machine I bought had the ability to switch between three major families of alloys: ferrous (steels), nickels, and coppers. Also, the carbon analysis was a bit steadier than past generations of machines, but I still trusted the old LECO carbon analyzers for reliability.
Lastly, you state the spectrometer will be lab based. Let me state the importance of lab cleanliness (with any type of spectrometer). Both labs I've dealt with had positive-pressure rooms for the spectrometers. Also, the air filtration system and temperature of the lab were kept under control. One of the labs sat no less than 25-feet from the induction furnace that was melting the alloys! Needless to say, I not only worried about cleanliness and temperature, but also the vibration and harmonics the furnace produced. (We had a floor dampening system installed.)
And I agree with arunmrao. I'd buy nothing from China in this case. Stick with the known entities: Baird, ARL, SpectroAnalytical (just to name a few). That warning also goes out for other "developing" countries.
Whew! Sorry to be long winded, but believe me, I know what a chore in a steel mill or alloy mill that keeping a spectrometer up can be. Just trying to pass along that knowledge. So, if you have any more questions, don't hesitate to ask.
Good luck!
~NiM