Having a hard time identifying some FET's in a blown amplifier
They are NPN and PNP power transistors 2SD998 and 2SB778.  Datasheet http://pdf1.alldatasheet.com/datasheet-pdf/view/734001/JMNIC/2SB778_15/+W34Q2_VhlMpEcBVhDEGuzG+/datasheet.pdf

And 
http://pdf1.alldatasheet.com/datasheet-pdf/view/270403/SAVANTIC/2SD998/+Q51W25VPvuCOUlheY/1lHpp+/datasheet.pdf