Really, I would spend the extra 20-30 bucks and grab the 930. Why? Because the 930 uses the 65nm cores as opposed to the 90nm cores, which means less heat and power consumption in general. I haven't seen a direct comparison of the two processors, but I'm guessing that the 930 also has less power consumption than the 830. They are both the same speed and have the same FSB, which is good, and the 930 has an extra megabyte of L2 cache per core, which equals two times two megabytes or four total, whilst the 830 has one times two or two total. So, that will also give you a performance increase. If you are on a budget, go with the 830. If you have a little extra money to throw around and you want a bit nicer setup, go with the 930. Even though you probably won't notice a huge difference of speed between the two, the new 65nm process and the extra 2 megabytes of L2 cache are just cool to have.
But, do what feels right.