wekiller , it really depends on the processor chip. Some chipsets supports upto 4GB, some maybe more or less. So if you happen to have a chipset which supports lesser, adding an additional memory chip would not increase your capacity. It might even cause problems for your player.

However, most flash based players use Nand Flash memories. There is a good guide on the soldering process at the S1mp3 wiki here http://wiki.s1mp3.org/How_to_add/change_a_memory_chip