I'm new here :)

You could either use the accessory lead off the ignition harness to power your extras, or you could use a relay as customsuburb suggested.  If you used a relay, and I'd use 10 gauge at the most, but probably 12 gauge.  There's really no need for anything bigger, because you're drawing less than 10 amps max for those accessories and trying to connect 8 gauge wire to a relay wouldn't be fun.  Yes, though, the way you have your relay configured would be correct.  I'd fuse everything separately.

For your alternator, a 200 amp fuse would be fine.  Just like you said, you're not going to draw anywhere near this much.

wow...thank u so much geepherder. i really owe u...u were all patient with my noob-ness and everything. i know for sure that there probably isnt anything in car audio that i know more about than u, but if u ever do need any help and if i can help in ANY way, plz let me know :-)

thanks bro

-mir

ohhh i forgot to ask u. geepherder, im sure theres a few different wires in the ignition harness (ignition, accessory, etc etc). is the accessory wire (that keeps accessories on when the car is off but the key is in) different from the ignition wire (that keeps the accessories on when the car is on)? if so, do i have to upgrade both of those wires or will upgrading the accessory wire take care of it?

thanks...

The difference between the accessory wire and the ignition wire is the ignition wire retains power while the starter cranks.  An accessory wire will lose power while the starter cranks in order to supply all available juice where it's needed most- the starter.  Don't worry about upgrading these wires, though.  If it makes it easier for you, just tap the accessory wire at the radio to control your relay.  Yes, as customsuburb said, you need to ground all your components.

thank u so much bro (geepherder and customsuburb)

when i have everything together, imma take some pics and show u guys. u were a big help...again thanks

-mir