When you say squeezing the most performance from it, are you planning on overclocking or not?
If not, you will get essentially the same performance from any motherboard - even when overclocking it's unlikely there will be much difference unless you're talking about extreme overclocking. (i.e. not a workstation, but a hobbyist who can put up with downtime)
That said, ASUS is generally a reliable brand. (though their P67 boards had some issues)
For cooling, I would probably look to Noctua. I went with Corsair's new quiet series fans this time around and they're louder than I would like, even with speed reducers.
Apparently Noctua have solved the problem of PWM fans audibly pulsing, but I can't confirm that myself.
I generally can't stand PWM fans, but PWM is a lot better in theory (more energy efficient, and allows for lower speeds without stalling) so if Noctua have solved it, that would strongly put me in favor of them.
With a Z-series chipset, have you considered SSD caching rather than a large SSD? I have a smaller SSD that I use as my boot drive on a P67 board, and that's one feature I wish I had.
When used as a boot drive, there's a lot of data on the SSD that really doesn't have to be, because it's accessed so infrequently (if at all) and I'm always finding myself moving files back and forth between the SSD and HDD. (this happens a lot with games, which may be 20-30GB each, and are one of the tasks which seems to benefit from an SSD the most) At 512GB, that's certainly going to be less of a problem though.
I don't know that I would be wanting to spend much on an SSD right now either, as drives have been saturating the SATA3 bus for a couple of years now (theoretically 600MB/s, realistically around 540MB/s) and if Apple's recent announcements are anything to go by, we may be starting to see a shift towards PCI-E drives. The new MacBook Airs, which are Apple's consumer line of notebooks, are reading data at just under 800MB/s.
As for RAM, some tasks do benefit from higher speeds, but generally as long as you have 1600MHz (I don't think that has changed since Sandy Bridge) you will have virtually identical performance in most tasks.
The latest Intel designs don't really seem to benefit much from faster RAM, as long as you meet the specification. (below 1600MHz, performance drops quite a bit)
It may make more of a difference if you are using the Intel HD graphics, rather than having a dedicated graphics card though.
Generally fewer sticks of RAM are more stable. Haswell is still dual channel, so you want to be adding in pairs though.
I have 8GB in my machine right now, but would probably be looking to get 16GB for my next upgrade. (or possibly 32, using four sticks)
With an increasing number of 64-bit applications, there are times where I'm pushing the limits of 8GB.