Fan placement help -P180

I'm replacing all the stock fans in my P180. Here is what I currently have:

Sythe S-FLEX (1600 RPM, 63.7 CFM, 28.0 dBA) x1 -currently on my heatsink
Apevia (1700 RPM, 63.85 CFM, 29.67 dBA) x1 -currently in 2nd middle slot
Sythe S-FLEX (1900 RPM, 75 CFM, 35 dBA) x4

I'm going to use two of the 1900 fans for the exhaust (back and top), but am having a hard time figuring out the best placement of the other four fans. The slots I have left are the heatsink (120 ultra extreme), the two middle intake, and the bottom one between the hard drives and the psu. I have 4 hard drives down there but it doesn't really get too hot. I'm doing this now because my Q6600 (3.0GHz) is idling around 48-50 and hitting 65 under full load when it's running BOINC at night because of this damn heat (its about 90ºF out and my air conditioner is broken )

I'm thinking of putting one 1900 in the heatsink, one 1900 down below, the Sythe 1600 in the front of the middle slot, and the 1700 Apevia behind it.

Or I could stick the two 1900's in the middle slot, the Apevia down below, and keeping the 1600 Sythe on the heatsink.

What do you think?

I had thought of putting another fan on the heatsink but decided to wait until I needed something at newegg so I didn't need to use rubberbands (they are selling clips for $1.50 with $7 shipping).

The middle area was what was bothering me. So there really isn't any benefit to a second fan there? Would it be better to have it closer to the front for intake, or closer for blowing on the graphics card?