New system fan question

Hey guys just got a new system and was wondering about fans and temp.i have antec 300 case which comes with two fans one on side one on rear.My CPU is i5 2500k GPU is asus hd7870 dc2-2gd5 mobo is gigabyte s.115 intelz77 atx 4g ddr3 memory and antec 650 continous psu.

I noticed i could feel a slight breeze coming from my fans but could not really hear them.I am using this system for gaming and it has been working great but i am worried about temps.I just got speedfan and my gpu is sitting at 30c when not playing games when i increase % in speedfan i can really hear it go but when i increase all the other ones nothing happens.Can i only increase speed of my GPU fan and not case fans?The fans say 3 speed on them.I was also wondering what i should put my gpu fan at for gaming.

Any help would be great.I do not make alot opf money and this comp was a big investment for me and want to make sure i take care of it.Thanks again