here I give only my point of view, without much element to proove it.
mainly, it is difficult to explain all the elemnts that made me go this way know (and even if may be I change this within one or two or three years).
I would take as many cores as I can : may be 6 instead of 4.
and 4 instead of 2.
=> apache, and mysql, ... are not using the same thead. even for the same request of the user.
plus, there are all the small process that run in the mean time, on the machine.
so, to get some speed/power, take advantage of parallel processing there.
I would take a AMD instead of intel.
cheapest.... or to be precise : best quality and power for the price.
I have read intel delivers more speed per dollar.
I would not take an APU of AMD.
the "A6" or "A8" series, with the socket FM1.
those "Accelerated Processing Unit" are some kind of bundle of Graphic processor and CPU.
that is good for PC for game.
... hence, you don't need this kind of new architecture.
Some comparison shows that the Phenom and the FX series are much more powerfull than the "APU" series.
this is normal : APU do some graphics... you cannot expect same result for those that do some graphics + processing.
Definetly would take a SSD and a Sata 3 mother board.
access to the disk has been the bottleneck of PC and small servers for years.
it might start to be resolved... with those two things.
And keep the disk (regular HD) you have yet for not vital things of the machine.
(backup of course, but also things that do not need speed...).
SSD : 120 Go : they are much faster than the 60Go, since they are made of 2 chunks of 60Go, that are working in parallel (with the controler that does that... but now it seems that the SandForce controler... is doing it... as most of the controlers of the recent disk).
I like the OCZ Vertex 3.
it is a bit better than the other, for writing.
so, as you will write a lot of logs, a lot of DB, a lot of new code for new dev versions.... the good writer are better.
(avoid the usual benchmark that put in front SSD that read fast... for people that looks at films...).
whatever SSD... take a SSD,... this is a jump in speed of computers.
Sata 3 is good for transfert rate.
Sata 2 is ok two.
I used to take the best, such as the Tagan that were really great when they appeared.
now, some seasonic, for the silence (my machines are also quiet ones... as I live with them...).
but... next buy (next week or so for my new machine) will be a very simple Advance box with psu 480W include, for 55Euros... and will see.
long time ago, I used to have no name psu.
I want to give it a try again... because when it come with PSU, I really feel that there is a lot of fuss about it (especially with the powers... such as 600W ... ) and that some basic noname might be far good enough.
the only focus I will have is the quality for the low consommation and high efficiency on energy matter.
well, that is only my point of view.
hope it helps.