any suggestions on my build

If you have 4GB of RAM installed, you will want to select the 64 bit edition of Vista. Other than that, looks good. 

Because the 32 bit version of Vista can only use a little under 3GB of that RAM. 64 bit does *not* "require" 4GB of RAM, 64 bit is required to gain the ability to address 4 GB of RAM.

As to why?

because...

2^32= 4294967296
4294967296=4GB

That is the limit of addresses in a 32 bit operating system. This is to include the addresses the operating system itself needs to inhabit, the addresses for all physical hardware, and all memory on that hardware. By the time you get done ripping chunks of addresses away for those things, the typical user is going to be looking at between 2.5GB and 2.85GB of addresses remaining for system RAM.

Microsoft apparently got tired of answering the phone calls and emails from people demanding to know why, if their motherboard supports 4GB of RAM, Vista 32bit won't recognize it. So instead of reporting how much RAM your system can actually use, they now have the system page display how much RAM is installed. 2^32 hasn't changed, and neither has the capability of any 32 bit OS to address RAM, regardless of what that last patch to Vista would have us believe.