been trying to read up on transistors , but i'm kinda lost...

bassicly i'm trying to "learn" an car audio amp , but there's 1000's of transistors ...i eventually want to build a mosfet with quite some power to it... i understand that there are P and N transistors and i do understand the workings of the transistor a little bit.however i don't understand the values of a transistors like

- Drain to Source Voltage (Vdss)
- Current - Continuous Drain (Id) @ 25° C
- Rds On (Max) @ Id, Vgs @ 25° C
- Input Capacitance (Ciss) @ Vds
- Gate Charge (Qg) @ Vgs
- Gate to Source Voltage (Vgs Max)

some transistors don't have values in some tables like the pair K1058,J162

http://search.digikey.com/scripts/Dk...;keywords=J162
http://search.digikey.com/scripts/Dk...keywords=K1058


* what does values in a transistor determine if it would be a right one for an audio amp ?

* does the rail voltage effect the type of transistor chosen ?

* what effect does load impedance have on the type of transistor chosen ?

can someone explain this to me in normal english without getting to technical about it ? unless you absolutly have to to explain it... i tried books but they are confusing to read.

http://members.tripod.com/valveaudio.../mosfet115.JPG

i learns mostly by association and by doing things , i'm not much of a learner from books. btw above schematic is the one i'm trying to "learn"