From the looks of it, you should be fine. It will highly depend on your internet connection though. I ran mine on about similar specs except I was running on Ubuntu 12.10 (which likely requires significantly less resources than Windows 8). I will warn you though to get rid of Mystcraft early. If it is like mine, the comp will not handle people loading worlds left and right. I have also found that switching to MCPC+ as the loader will decrease lag significantly. But overall, if you ran vanilla, you should be fine.
