I would personally go for a 700w, that little bit of headroom is always nice...

er did I? Are you sure?

anyway thanks for the ideas.. keep them coming

You would be surprised at how little power stuff uses.

Going from that power usage calculator website this set up will use around 336W of power meaning 525W is probably about optimum for the set up.

Going for a 700W PSU is overkill and will reduce the efficiency of the PSU making it more expensive to run.

How do you work that out? The efficiency of a PSU doesn't vary with load - if it's 80% efficient drawing 300W it'll still be 80% efficient drawing 600W. There may be a slight variation with temperature but it'll only be small.

Also, the wattage rating is the sum of all the lines - if you have a lot of draw on the +12V line you may run into problems with the amperage - you need at least 18A on the 12V line.

According to the 80plus website the efficieny can change as much as 5% or more given different loads and they are most efficient at aroun 60ish% load.

The harder the PSU works, the less efficient it gets - as you say it gives out more heat - heat is just energy that is being wasted. 100% efficiency would generate no heat.

This is the table from 80Plus:

Fraction of Rated Load 20% 50% 100%
80 PLUS 80% 80% 80%
80 PLUS Bronze 82% 85% 82%
80 PLUS Silver 85% 88% 85%
80 PLUS Gold 87% 90% 87%


So at worst the difference in efficiency is 3%, and the most efficient point is at 50% load, so id your PC needs 350W, a 700W PSU will be the optimum one.

I was going by looking at the graphs of the output from the various PSUs.

Oh well, get the best you can afford and it'll do you well. But the 700W PSU will give you a LOT of room for expansion.

Remember that overclocking a 920 to 4GHz will up it's power consumption to around 300w.

Get the biggest best psu you can afford.

right heres my first stab

Intel i7 920 £199.15
Asus P6T Deluxe V2 £198.00
CM Storm Scout mid £74.97
6GB C XMS3 DDR3 1600 £140.27
750W Blue Antec Truepower £98.06
Artic Cooling Freezer £18.39
GTX275 Gainward £175.92
640GB WD Caviar Blue £43.69

Total cost:inc Vat +delivery £960.71

Change the cooler to the Fenrir Titan. It's much better especially at 4GHz

Go for the P6T SE and buy a better GFX card?

...and a pair of ear defenders. The Twin Frozr GTX275 gets noisy even with the fancy twin fan heatpipe cooler on it. I dread to think what the stock one sounds like.

The P6T SE only supports missfire if I recall from when I was looking, not SLI. The P6T supports both however.

There's not a lot of room left in the budget for a better card when you put the cost of a decent cooler into the equation. The only worthwhile jump from the 275, the 285 is more expensive and only marginally faster and the 4890 is noisy pile of meh. There is the 5870 and that is £150 more, or the 5850 is £220

This was my stab from Overclockers:

OcUK Value GeForce GTX 295 1792MB GDDR3 PCI-Express Graphics Card (Dual PCB) £289.98
Intel Core i7 920 D0 Stepping (SLBEJ) 2.66Ghz (Nehalem) (Socket LGA1366) - OEM + Operation Flashpoint: Dragon Rising Game £199.99
Gigabyte GA-EX58-UD3R Intel X58 (Socket 1366) PCI-Express DDR3 Motherboard £142.98
G.Skill Trident 6GB (3x2GB) DDR3 PC3-16000C9 2000MHz Triple Channel Kit (F3-16000CL9T-6GBTD) £132.99
OCZ ModXStream Pro 700w Silent SLI Ready Modular Power Supply £74.99
Coolermaster Sileo 500 Silent Case - Black (NO PSU) £66.99
Samsung EcoGreen F2 1TB SATA-II 32MB Cache - OEM (HD103SI) £55.98
Titan TTC-NK85TZ Fenrir CPU Cooler (Socket 754/939/940/AM2/LGA775/LGA1366) £25.99

Total : £1,004.26 (including VAT and Shipping)

Some comprimise to get a better GFX card but they're justified IMO. I would certainly have a plain case and a top GFX card! e.g.

The Samsung Eco Drive is 5400rpm but actually performs the same as a 7200rpm drive in tests
Others have the Gigabyte board running a 920 at 4GHz so no worries there
I use G.Skill RAM and think its very, very good
CM case is sound proofed and cheap