If you live in a city with a Microcenter you can save at least $70 off that AMD 4100/Asrock 990 Extreme 3 combo over newegg prices. If you *must* get it from newegg, save $10 by ordering the CPU/mobo as a combo -
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.1067398 I think that's the same board. Although look carefully at benchmarks, I have not tried one but from what people have been saying the 4100 is almost the same performance as the Phenom II X4 965 Black, also on sale at newegg/Microcenter for $80 or $90.
I presume you're going to run a 64 bit OS, otherwise 3/4 of that RAM will be wasted. Don't pay a ton for 1866 ram if you can find cheap good-quality 1600 ram, it's just not gonna make that much of a difference. you'll see WAY more performance difference from a $40 better CPU than a $40 premium buying 1866 ram over 1600.
The power supply is overkill for what you've got, but I guess not if you're thinking of getting a 2nd GPU. Don't cheap out on the power supply however tempting it may be - stick with Seasonic or the Corsair/Thermaltake/NZXT/etc specific models that get a good review on jonnyguru.com
I would forget water cooling for now, it's a big hassle. If you want the performance, spend the $$$ you'd blow on water cooling and just buy a better CPU - it's just not worth buying $80 of gear to overclock a $100 cpu.
Yeah if you do get an SSD you'll have a lot less hassle with a 64G one, I was able to live with my windows XP partition at 20G by never ever EVER installing anything else in there, but those days are gone. All kinds of crap insists on installing in inconvenient places deep inside your windows directory *cough* Chrome *cough*.
The 4100 isn't the GREATEST gaming cpu, but it's OK. AMD is supposed to be releasing a new generation of CPUs any day now so you might wait to either see how that shakes out either with better performance for the $$$ or discounts on the current generation. Fake edit: I see news stories on "Piledriver" and it looks like another disappointing release
For a gaming cpu I'd be seriously looking at Intel - the Microcenter combo of $170 or so for an i3-3225 + Asrock motherboard is just too tempting to pass up (I sound like a microcenter ad but their combos are scary good - but in store only
) And having the Intel socket 1155 gives you more headroom for gaming cpus - i5 3570k is only $190 and that's a LOT of cpu power.
Cases are kind of a personal thing, but I mostly wait til something I like is a current free-shipping special on Newegg or Amazon.