Hello All,
Recently I built a new pc, with the following specs:

  1. Ultra Aluminus midtower case
  2. ultra xpro 600watt power supply
  3. core 2 duo e7200 with stock fan
  4. 2gb of pny ddr2-800 ram
  5. gigabyte P35 motherboard (very stable)
  6. HIS Radeon HD2600Pro Graphics Card 512MB DDR2

Ok, now to the question:
I have a core 2 duo e7200 w/stock fan, and with my large case with cpu air duct and ventalation, as well as decent cable management, my cpu and pc runs really cool. My cpu does 36*C on bootup , 40*C on idle, and (according to core temp), ~60*C on full load with both cores at 100% load. I have no case fans installed. I have a spare 120mm case fan which i was using for an intake fan(wouldn't mount on the back with the screws i had for an exhaust fan), but the pc sounded too loud. So, i took it out, and no temperature differences were noticed. Are the temps that i am getting good for now (i will get a 120mm exhaust fan in a couple of months), or do i need to put that intake fan back in. I would hate to have to deal with a noisy case, it sounds like it is not there without any case fans. Please note that i do have vga card ventilation, cpu air funnel on the case, a psu that sucks out hot air from the case, and a power efficient cpu with a nice and quiet fan with speed step enabled. Thanks to those who can help.

You need a rear exhaust fan otherwise the PSU will suck in CPU cooler exhaust. While CPU and ambient temps may be OK, PSU will run hotter affecting its life and stability. You'll probably be OK as long as side panel is removed.

at those temps it sounds ok... i would at least put an exhaust fan in though. i agree with willcomp. you need to draw the CPU exhaust away from the PSU. even with the exhaust funnel on the heat sync the hot air will still get sucked into the PSU.

i put an exhaust fan a few days ago, and i am safe for now, i will buy a real 93cfm or 76cfm case fan and use the current one as an intake