Need help with CPU temperature being too high

in 2009 or 2010 I bought a Dell Studio XPS 435mt, it's an i7 920.

The motherboard is dx58m01

Since buying it the CPU fan has been stupidly loud, this isn't anything new, however I've recently become fed up with it and decided to do something about it. The CPU, when idle is around 71C.

A year ago I bought a new gfx card that wouldn't fit in the tiny Dell case so I moved everything to a much bigger case.

In the past 24 hours, this is what I've done to try and get the temp down:

new ultra quiet CPU cooler, the heatsink is so big the side of the case no longer fits
http://www.cclonline.com/product/26461/CNPS10X-Performa/CPU-Coolers/Zalman-CNPS10X-Performa-Ultra-Quiet-CPU-Cooler/CLR1030/
New silent PSU
http://www.cclonline.com/product/42158/PC-650AUBA-M/Power-Supplies/650W-Powercool-High-Efficiency-Power-Supply/PSU1188/
new case fan

the PC is now silent, which is great, however, with the side of the tower on or off, with the PSU inside or outside the case, with the old gfx card or the new high power one, the idle temperature is still 71C (CPU temp), when under load it's around 90C

I've reseated the CPU, cleaned & re-done the thermal paste twice, confirmed temp is on C and not F, tried in our house which is very cold and at work which is a normal office temp and I always get the same results.

I'm assuming it's always been high and that;s why the old fan always sounded like it wanted to take off whenever I did anything. The BIOS tells me nothing at all to do with fans or temperatures (BIOS is pretty much useless)

If anyone could help me with this it would be very much appreciated.