Water cooling doesn't need to be super expensive. Phase is not a good example, phase is for serious overclockers. Water cooling is all relative. From a simple CPU block pump rad and t-pipe to very high end kit.
A very simple set up can be put together for around a £100. Cheaper if you use second hand components. I'd say a reasonable setup CPU,GPU,240Bix rad, pump, res and tubing can be done for a little over £200.
With that you'll see a the temps drop on the CPU to below what air can do, but the GPU you'll notice more. I'd say you can expect the CPU to drop 5-10 degrees but the GPU can drop upto 20-30 depending on the GPU and block.
That's my experience anyway, I've been water cooling my PC's for the last 5-6 years, ever since the XP athlons. I won't go back to air now. IMO, water cooling is a must for me. My PC is a lot cooler running and and a hell of a lot quieter. Especially with the newer high end GFX cards cooling solutions
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Brigstock