I haven't seen any Z88 motherboards.
Z77 are the most feature packed boards:
http://en.wikipedia.org/wiki/LGA_1155#Ivy_Bridge_chipsetsZ75/Z77 allow OC'ing. It also has the most amount of PCI-express configurations. Some other chipsets are 'business' users only, though.
In your case, a H77 may be sufficient if you don't plan to OC/build extensive PCI-e configs. Moreover, if that's the case, a plain 3770 may be sufficient too.. (only the i5 have the GPU difference I believe)
The coolermaster case seems a reasonable choice. It has a very similar style and approach, but is cheaper. Personally I didn't like the big logo sticker on the front screaming "Look at me, I am a cooler master PC".
The problem with aftermarket coolers they often are a bit fiddly to install. The boxed cooler can be installed from the front with some clips, but for example my Mugen 2 has a backplate. Fortunately this Fractal case has a removable side panel + cutout in the motherboard tray. But even then, I find it easier to install coolers outside a case.
Ah well, generally a cooler with heatpipes + large lumps of aluminium plates is good. Some coolers can be gigantic, but feature 120mm fans that can cool the CPU at reasonable temperatures (without OC) at low-mid speeds.
On my previous Q6600 the boxed cooler was pretty horrid. It ran full speed at full load from day 1. After 2-3 years the paste dried out, which is pretty remarkable in itself.
I don't have experience with the boxed cooler on Ivy Bridge CPU's. Of course it will work, it's not essential or something.
About RAM: yes some apps use more RAM when you got it. On my old laptop I use 2GB out of 3GB with some programs open (Visual Studio, some chrome tabs, Skype, etc.). Same setup on this system runs 4GB + 2GB RAM disk (total 6GB)