Well, you've got enough hose running from the GPU there to (easily) put in another rad at the bottom. Just need enough height clearance.
An XT45 would require a little over 71mm (46mm rad + 25.4mm fan) , an EX240 which is shorter would require 61mm (35.5mm rad + 25.4mm fan)
You'll probably have to slide out the PSU a bit to make it easier to mount the rad & connect the hoses.
Oh, and since this is in the bottom of the case, some decent fans on the rad can be used
The only thing i see is re-filling being a bit awkward. In order to avoid trapping air in the top rad, it needs to be unbolted from the roof and turned and lowered so its more or less vertical (the ports at the top) AND the ports lower as the reservoir. Once all air is out it can be lifted again and bolted to the roof again.
This is why it is easier to use one of those multiport rads like the Alphacools & the XSPC EX & RX series. It allows for one of the ports to be used as fill/vent
The AX are good rads, but they should always be mounted lower as the res.
Anyways, idle temps at +40°C for CPU + GPU are a bit high, especially since MB is 36°C.
This indicates that room temp is probably 23-25 °C and ... that
you don't have enough radiator... the CPU gets warmed up by the "idling" GPU's.
On prime the CPU alone reaches almost 80°
-which happens on prime, but you really want to avoid that- and it that case the 360 puts up a very good fight. The 360 rad has no problems handling the CPU alone or with the CPU loaded while the GPU's are idling.
However, if you would run the Heaven benchmark on the GPU's alone, they will most likely overwhelm the 360.
In real world application like gaming you'll have above average load on the CPU
(not enough to go to 80°C, but above 50°C definitely) and some more load on the GPU's.. and they will tend to go to 80°C.
(if you want to keep the GPU's in check, go easy on the MSAA, PhysX & other hires-quality aftereffects and set VSYNC to ON)
The combined CPU + GPU's heat load is too much for the 360 and the CPU will run too hot as it gets heated by the GPU's.
You can try to up the performance of the 360 by taking IN air from outside the case AND put some serious fannage on it.
But ultimately, you want another rad in the loop. A 240 will bring your total raddage up to 120.5 which is about right for a setup like this.
The simplified rule of thumb is 120.1 for CPU + 120.2 per GPU
(and 120.2 for CPU + 120.3 per GPU for "silent" running)
Now, having radiators IN the case comes from the idea "i might wanna go LAN party someday", as far as i am concerned.
If you never plan to go LAN party... just use something external like a MO-RA3 or Phobya NOVA. It allows for much smaller and quieter and nicer (and sometimes cheaper) PC cases. It allows for a nice mini/midi or mATX case on the desk and having a nice 120.9 rad next to it (or under the desk as a legwarmer)
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*i like this smiley icon*
