Does the HD matter for a gaming build?

If you want the game to boot faster, then yes a faster HDD would be what you need.

A faster HDD will load/start any program a bit faster than slower HDD. Is that a surprise?
After that? almost no impact to gaming performance, although levels will continue to load faster with a faster HDD.

Crysis Level load:
WD VelociRaptor 300GB 36.9 seconds
WD Caviar Blue WD6400AAKS 37.5 seconds
Price difference of that 1 second advantage? about $130

If your focus is purely on gaming, it really isn't worth investing in from a value point of view, since a faster HHD with 1/3 the size will only buy you a few seconds for a $50-$100 premium. Creds to WR2 for a specific example, although I would imagine there are others where the gain is much more noticeable. Still, not worth it in my opinion.

Now, when you put SSD into the mix, that small gain might change, but SSD's are still very expensive for the size (A quick look on Newegg shows that good quality/faster SSD's that have 80GB reach $250, and higher capacities get even uglier (256GB is $669!). You should really only consider SSD's for performance builds where either money is no object, or your budget for arguably more important parts of a computer (CPU, GPU, even the MOBO) wouldn't suffer from the added cost.

Case and point: for a gaming rig, speedier storage isn't worth it, and is on the bottom of your list of priorities. Bumping your rig from a 4770 to 3x4770 in crossfire, for example, will reap FAR more benefits than an SSD with pitiful storage.

Thanks for the advice folks, really appreciated.

Hard drive will just affect how fast your game will start and how fast stuff will load but in terms of actuall FPS, performance will not be affect since applications are loaded into the RAM so RAM is what affects it. However, if your Pagefile is heavily used it might affect, but I am not knowledgeable enough on how Pagefile works and how OS uses it to be commenting on it google might help.

True, and it's good to emphasize that difference; faster HD's and SSD's will only affect load times, not FPS or otherwise.

As far as RAM, you actually don't want TOO much... 4-6GB of fast DDR2 or DDR3 does the trick. You obviously want enough room for the OS, the game in question, and other programs to operate with some breathing room, but if you give too much room you put a strain on the CPU and, in effect, bottleneck it's performance (I personally think that any amount of RAM beyond 12GB is wasteful for 99.9% of users).

As for Pagefile, I have no clue... anyone an "expert"?