if the case has a fan in the back, under the psu(different from the big one in some psu) put it to take out the hot air, sometimes it comes installed to put air inside
also it would be ideal to test another psu, some brands just report fake values, a "600" w. psu is normally a 300 - 350 w. in reality, a thermaltake(and other good brands) is more stable, a 450/500 w. should be more than enough for that hardware
the cpu temperature values should be similar or lower on that cpu you have(compared to that 27° c)
do you have a way to verify that this temperature reported is real?
if you can touch the heatsink when the system is off you can easily verify this(don't do it with the pc powered on, do it with the psu disconnected from the wall, no electricity), just after having it under load
some mainboards can report erroneous values(usually sensors dying, time to replace board usually)
some cpus can report the temperature value based on other values/parameters(front bus, clock speed, overclocking) and a wrong setting can give wrong temperature values, reset your bios could help if the other steps doesn't work(including new thermal paste)