Gaming at 4K is fluid enough only when using Crossfire or SLI setups. And even those are not able to run current-gen games with maximum settings. Have a look at this review for instance: Watch Dogs Performance and Image Quality Review
. Or here: Watch Dogs review: tested with 32 GPUs
.There are no fanless solutions for cooling even one of those top-of the line GPUs, so a fanless dual top-of-the line GPU setup is not possible either.
If instead of gaming, what you want is to have the PC desktop at 4K, and even to watch movies at 4K resolution, then this is possible, but there are some things you need to consider:
1. 4K @ 60 Hz (for PC desktop) is possible only through DisplayPort 1.2 and HDMI 2.0 connections.
All present-day motherboards and graphic cards that have DisplayPort outputs, are version 1.2, so that's ok. However, there is no motherboard or GPU with a HDMI 2.0 output, and according to known Intel and Nvidia/Amd plans, this will not change in the near future either - Broadwell will not have such support, the soon to be on the market nVidia GTX800 cards will not have them, and no such plans are know from AMD, either. So, DisplayPort 1.2 is the only option, an will remain so in the near future.
Regarding display types, you're ok if you plan on using a 4K display monitor, since these have DisplayPort 1.2 inputs. But if you want to use a TV, then you're again limited - the only 4K TV sets that have DIsplayPort inputs, are the Panasonic 4K TV sets. All the other big brands: Samsung, Sony, LG - offer only HDMI inputs (and even those are not all HDMI 2.0, or do not support all that's needed from a HDMI 2.0 port in order to be future proof).
2. 4K @ 24 fps (movies) is possible through DisplayPort, HDMI 2.0, and existing HDMI 1.4 connectors. Current gen motherboards and GPUs have DisplayPort 1.2 outputs, and the HDMI ports are very likely 1.4 - which should allow you to view movies at full resolution.
3. Available 4K video content is somewhat missing - and when you do find some, it's usually encoded with H265. Again, there is no hardware support for full hardware accelerated H265 decoding in current-gen hardware, and there is no support planned in the near future either. Just like with the support for HDMI 2.0, neither Intel, nor the GPU manufacturers have announced full hardware H265 decoding acceleration. That means you will have to rely on the CPU for decoding, and depending on the bitrate and encoding options, it could be either ok, or not ok at all: 4K H265 video decoding can either be very light on the CPU, or can use 25% of an i7 4770 or even more. Still, this means that a passively cooled current-gen Haswell CPU can be used to play movies at 24fps, so at least this is possible.
This is just not the right time to look for future-proof 4K hardware, I'm afraid.