The 430W Eco only has one PCI-E cable and the 280 requires two.
It's a slightly more powerful card than the 960 but the 960 is what I'd go for here. Much lower TDP for that case, the fans will have less heat to cool, so it'll be less noisy. Plus the passive mode up to a certain temperature (55/60C or so). Some games won't even stress it that much.
Pentium-K v i3, it's a tough one. Pentium-K does better in single-threaded games. Two thread games and it can start to struggle with other processes going on. i3 does better in games using more threads.
Deus Ex seems to be a game that uses more than two threads but doesn't need too much GPU power, for instance.
http://techbuyersguru.com/CPUgaming2.php
To be honest Phil, if you really want no compromises noise-wise then let me show you a £700 spec that covers everything except an Intel quad-core i5. And then make compromises if you need to to bring it down.
YOUR BASKET
1 x
Asus GeForce GTX 960 DirectCU2 OC Strix 2048MB GDDR5 PCI-Express Graphics Card £169.99
1 x
Intel Core i3-4160 3.60GHz (Haswell) Socket LGA1150 Processor - Retail £99.95
1 x
Samsung 250GB 850 EVO SSD 2.5" SATA 6Gbps 32 Layer 3D V-NAND Solid State Drive (MZ-75E250B/EU) £89.99
1 x
Microsoft Windows 8.1 64-Bit DVD - OEM (WN7-00614) £77.99
1 x
Silverstone SFX-L 500W '80 Plus Gold' Fully Modular Power Supply £74.99
1 x
Asus H81I-Plus Intel H81 (Socket 1150) DDR3 Mini ITX Motherboard £58.99
1 x
Silverstone SST-ML07B Milo Mini ITX Case - Black £51.95
1 x
TeamGroup Elite Black 8GB (2x4GB) DDR3 PC3-12800C11 1600MHz Dual Channel Kit (TPKD38G1600HC11DC01) £41.99
1 x
Noctua NH-L9i CPU Cooler Low Profile - 92mm £34.99
Total : £710.42 (includes shipping : £8.00 Ex.VAT).
500W SFX-L PSU with larger and quieter 120mm fan than typical 80mm SFX. The max load on it with that system will be about slightly less than half-to-half, so the fan should only spin nice and slow.
960 with half the TDP of a 280, quiet cooler, and fans' passive mode up to certain temp.
Quiet Noctua cooler.
Only way I can think of to get that even quieter is fanless PSU (very expensive) and fanless CPU cooler (expensive and most won't fit in the ML07). And both would be a bit overkill, as a PSU that isn't stressed and a good, quiet CPU cooler like the Noctua achieve great results for a lot less cost.
Now £600:
YOUR BASKET
1 x
Palit GeForce GTX 750TI KalmX SILENT 2048MB GDDR5 PCI-Express Graphics Card £119.99
1 x
Intel Core i3-4160 3.60GHz (Haswell) Socket LGA1150 Processor - Retail £99.95
1 x
Samsung 250GB 850 EVO SSD 2.5" SATA 6Gbps 32 Layer 3D V-NAND Solid State Drive (MZ-75E250B/EU) £89.99
1 x
Microsoft Windows 8.1 64-Bit DVD - OEM (WN7-00614) £77.99
1 x
Asus H81I-Plus Intel H81 (Socket 1150) DDR3 Mini ITX Motherboard £58.99
1 x
BeQuiet SFX Power 2 400W '80 Plus Bronze' SFX Power Supply £53.99
1 x
Silverstone SST-ML07B Milo Mini ITX Case - Black £51.95
1 x
TeamGroup Elite Black 8GB (2x4GB) DDR3 PC3-12800C11 1600MHz Dual Channel Kit (TPKD38G1600HC11DC01) £41.99
Total : £604.43 (includes shipping : £8.00 Ex.VAT).
Stock CPU cooler. You can improve noise results by smoothing the fan profile from within the BIOS. The default profile is quite steep and you hear the variations in speed more that way. Notch up the minimum RPM slightly and lower the max RPM slightly and you'll get a more gradual fan gradient.
Lower wattage PSU. Should still be quiet as 750Ti has half the TDP of the 960 so the load range will be about the same, proportionally.
With this £600 spec you could choose the Pentium-K over the i3 if you wished, to fit the GTX 960 into budget. If so, then also decide whether you want the 500W PSU (for the reasons I mentioned earlier) or keep the 400W.