The 4" combo can fan will work great full blast or a 6" with the speed control on it which is cheap and makes a huge difference (they are loud all the way up) an even better fan imo would be the Vortex fan if it's available where you are shopping, they are much quieter than Can Fan but 6" is the smallest they make I think and no combo with the Can filter, definitely get a speed control too. Just exhaust right out of the tent with it and the hot air is going to go out through the carbon filter and cool air intake from the bottom vents..what are these LED panels you are going with? I hope they are'nt those cheap chinese ones man, big waste of time and money with very small yield...you might be better off with a procyon 100 for $550 - $595 (equal to about 250 watts HID) if the Lumigrow ES led light is too much money at $1299 (really equal to nearly 600 watts HID) worth every frickin' penny though both of them. Way better than 1 watt panels. Keep in mind your space would need at least 2 procyons or one Lumigrow ES to effectively illuminate that area of 4 x 2.