Just Looking For Suggestions to Tweak a New Build

I'm working on a new system which is going to almost be exclusively a gaming machine.

CPU: Intel i5-2500k
Cooler: Cooler Master Hyper 212
Motherboard: ASUS P8P67 Pro
RAM: Corsair Vengeance 4 GB
GPU: Sapphire Radeon HD 6870 1GB
PSU: Corsair 750W, don't know the model#
HDD: Western Digital Caviar Black 500GB
Case: In-Win Digital Lite BUC or Cooler Master HAF 922

Approximate Purchase Date: Within 2 months
Budget Range: ~$600
System Usage from Most to Least Important: Gaming, Movies/Streaming TV
Parts Not Required: GPU, PSU, DVD, Sound Card, Network Card
Preferred Website(s) for Parts: NewEgg, Amazon or TigerDirect are the ones I'm familiar with
Country of Origin: USA
Parts Preferences: Just Intel for the CPU, as I've decided on an i5-2500k, and so parts compatible to that.
Overclocking: Yes
SLI or Crossfire: Maybe
Monitor Resolution: 1920x1080
Additional Comments: I mentioned parts of what I was planning to use and someone said to get a different GPU, but I was actually given the listed card as a gift and am planning to cannibalize it. If it would be better to just outright replace it, I might consider it, but so far I haven't had any issues with it to begin with. I may crossfire it with another identical card, too. I don't know the model of the PSU, but I know it's Corsair and it's 750W, and I trust the guy who gave it to me that it's newish and I know Corsair myself, so I have no doubts that it will be a good supply.

I'm planning on keeping this build for between 3 and 5 years and it is almost exclusively going to be a gaming machine. In particular, I have these questions:

#1 - I see a Gigabyte Z68 board recommended most of the time, but from my understanding the only difference is that it can use the integrated video on the i5, which I don't care about, and SSD caching, which I may skip in favor of getting a moderately large SSD drive down the line. Given that, there doesn't seem to be a reason to get a more expensive Z68 board, or am I wrong? Secondly, if I need to down the line I can replace the 2x2GB RAM with some 2x4GB sticks, and it won't matter that the first slot is blocked by the cooler (From reviews I've read of the board). I understand that 4GB is enough for gaming now, and 8GB is overkill.

#2 - The Cooler Master HAF 932 was actually recommended to me, but I went to Fry's to actually see the thing, and I have to say - I'm not building a juggernaut here. The 922 was a lot smaller, but the case looked kinda cramped when I considered the 6870, which is a fairly large card. The guy at Fry's said he has a BUC himself and would recommend it instead of most of the other cases they carried, but they didn't have a display model and I can't really find any reviews or info about it. Mostly, I just want to be sure that the case can fit the CPU cooler and the GPU well.

#3 - I live in Arizona, so the ambient temperature here is generally a bit higher than average. Should I look at a liquid cooling system or, given that I'm designing (What I think is) a relatively simple machine, will air cooling be fine? The Hyper 212 comes up a lot, so I'm fairly comfortable getting that to cool the CPU.

And if anyone has a suggestion about a tweak or replacement part, I'm open to suggestions. I'm relatively at ease with computers, including BIOS/overclocking - I'm just not much of a system builder, so these are the parts I've come up with after diving into the abyss and mucking about for a while. More knowledgeable opinions are welcome.