hi guys, i'm guitarist and i want to buy some cheap and still resonable quality mixer, power amp and pair of maybe 15" loudspeakers with pair of subs for using in locales of around 100-150m2 size (where we usually play)...

now i know enough about what's like which brand, so i need you to help me with technical issues...
first, i really don't know much about connecting speakers, mixer and amp in terms of electricity and everything similar... for example i know that amplifier's basic power (at 8 ohms) is almost doubled when resistance is doubled by linear connecting of 2 spekers, which make resistance of 4 ohms (if they're 8 ohms speakers)... i assume that i didn't quite understand that part too so please have understanding :)

anyway, what should i look for in technical characteristics to match mixer, amp and speakers? what is most important? what should i look for in dB ranges and stuff like that... maybe it's better if someone could briefly help me in this matter, and let's assume that i know nothing :)

and i would appreciate if some could tell me where could i read some basics that i need to know on net, or maybe to tell me what book to read...

thank you in advance!