Building energy efficient gaming machine

Budget?

Gaming laptops can go from $700-$4000, so we need somewhere to start.

i5-3470
Asus, Gigabyte, or Asrock H77
2x 4GBs Crucial Ram
HD 7770
Corsair CX430
Cooler Master Elite 430

AMD A8-5600K Trinity APU: $110

Asus F2A85-M PRO FM2 AMD A85X (Hudson D4): $137

A few great deals on DDR3 2133 out there --- the ASRock FM2A75M-ITX FM2 AMD A75 (Hudson D3) Mini ITX would make a really nice LP system.

Forgot to mention needs to be compact as I only have limited space under the TV and I'm also trying to keep the budget down.
I already have an thermaltake element Q (220W PSU) but I will need to change the PSU if I'm going to install a radeon 7770 or 6850
I5 3450S (65w)
2X4GB DDR3
Asrock H67M-ITX 1155 mini-Itx
What you guys think?

If you are going Ivy Bridge for processor then I'd go for the H77 version of the same motherboard - http://www.asrock.com/mb/Intel/H77M-ITX/
It's not much more expensive and it supports faster ram, USB3.0 header (it's likely a new case will have USB3.0 on the front panel) and while entirely pointless at the moment, PCIe 3.0.
Having said that, you should investigate layout of a motherboard too, as some itx cases are really awkward for layout/access.
Also if you are really desperate for low power, the T-series processors are really low power but I don't know how much realistic performance you loose. 3420T and 3220T i3s are 35w.

Don't get low power processors.

It's a fool's game only for very specific niche situations where you have limited power supply like a solar powered or customized 1-off research builds (handheld computer), and is a moot point when you'd actually have power and just want to be efficient.

Speedstep will take care of the power during idle, and if you really want to save power just turn computer off or to sleep (s3).

During a load, the stats on articles written here show that it is more efficient to have the higher powered chip that will complete the work sooner and the total power consumed to complete the task will be less than the slow chip. If you have a power ceiling envelope, you can also always just underclock the chip.

Since this is a gaming machine with a video card, all real energy usage is thrown out the window already. Switching your light bulbs or other appliances will save you more electricity than the computer.

Good idea Rammy I can spear a few bucks to get the H77. And about the power consumption I'm more worried about the idle power draw cause its not only a gaming machine its also a NAS+HTPC so its on all the time. I looked for the T servies cpus but I can't find any so I will go with an S.

Generally speaking AMD's APUs consumes less power when idling, but under load (like playing a game) Intel Core i CPUs tends to use less power. For good performance at low power consumption I would go with an Ivy Bridge Core i3 CPU. Dual core CPUs are fine for games since the vast majority of games only use 2 cores. Going with a Core i5 will get you 4 cores and games that can make use of more than 2 cores will perform better. Of course an i5 will cost more and also use more electricity. So... Core i3 if you really want to cut down on power consumption, or Core i5 for better performance, but still have somewhat low power consumption compared to AMD's Trinity APU while under load.

As for a graphics card, I would go with the Radeon HD 7750, low power consumption, but good performance per watt and for the price. Off the top of my head, peak power consumption is around 46w so a direct power connection to the PSU is not necessary. I believe I seen one for as low as $90 after a rebate. The Radeon HD 7770 is not much more money (around $125 before rebate), I think it is about 20% - 25% faster, but peak power consumption is around 78w so a power connection to the PSU is required.

I've ordered Asus P8H77-I and Core i5-3450S now the question is do I get 6850/7770 (I'm limited to 1 slot cards) but if I want to do that I will probably need to change the 220W TT PSU (sfx) or if I get the 7750 I should be able to escape without upgrading the PSU although close to the limit.

Is there a faster video card without aux power than the 7750?

The two builds in my sig.

1st: Intel i5 3570T which is a low powered chips on a itx form factor motherboard.

2nd: AMD Trinity APU build.

no, that's the one you want. there are certain 7750s that are fanless which might be a benefit for your build, check it out.

7750 is the leader in terms of performance/watt

only the 650ti ties it, but this requires aux power
http://www.techpowerup.com/reviews/MSI/GTX_650_Ti_Power...

The HD7750 *Cape Verdi* GCN cores will be incorporated next year into the 28nm Kaveri APU with 'Steamroller' CPU.

Which will run in that Asus F2A85-M PRO FM2 AMD A85X (Hudson D4) motherboard that I linked above with the AMD A8-5600K Trinity APU.