Crucial Ballistix and Crucial Ballistix Tracer

After lots of time researching, I have determined I probably want to go
with a Gigabyte GA-P35-DS4 motherboard. I like mwave's interface, so
here is the url of the page I'm looking at:

http://www.mwave.com/mwave/viewspec....iteria=BA24220

I've decided to go with the C2D E8400 CPU. I like the idea of having
them assemble and test for an extra $10. Regarding memory, the board
supports DDR2 PC8500 (1066 MHz). A matching pair (1GB X 2) is what I
want. If I go with Crucial, my choices a

ballistix BL2KIT12864AA1065
ballistix tracer BL2KIT12864AL1065

After the rebate, the first is $24.25 less than the second. What is the
difference between these two, and is the difference in price justified?
And speaking of price, I am wondering why the CORSAIR TWIN2X2048-8500C5D
2gb kit is double the price of the Crucial.

I suppose the next step is choosing the video card, case, and power
supply... I'm just starting to look at these. Do I need to purchase
separate cooling fans? Regarding cases, any brands better than others?
Any brands I should avoid?