fwNES, written by Fan Wen Yang, supports a good number of mappers and has a very interesting user interface. It also emulates the Japanese Famicom Disk System addon (which requires the FDS bios ROM). It's sound support is very good. It supports all 5 channels and the extra FDS sound channels for Adlib, SB, and other soundcards. Pentium class CPUs should be able to acheive full speed.