Im going to tell you that is an expensive board in porpotion to your whole system. I wasnt an X2 fan so i know nothing of which DDR2 X2 board is good. I do know though that X2 boards were cheaper than good intel C2D boards and mine was a cheap but excellent board. It cost me 105 bucks so I'm willing to bet you can save yourself 40 bucks and find a good board for 90 bucks.
That way you can buy a 7600GT instead of the 7300GT. Now the 7300 is MUCH MUCH more powerful than the 7300LE but still cant hang with a 7600GT ot if you can find one a 7600GS. Trust me save some money on the board and get a 7600 card and you wont regret it. The memory isnt bad, you could save some money and get a few bucks cheaper ram becuase with Corsair you pay for the name alot these days and G.Skill or Geil are also trusted brands. Yet the XMS isnt a bad deal really and you'd only save maybe 15 bucks, In the end high quality ram is the last thing you want. Most ram runs great if it isnt DOA these days so best going with cheapest ram with good reviews that is still DDR2-800. That way youll be able to get a better card. I was going to say dont go AMD but I had no idea that the 3800+X2 were that cheap anymore so NM bout that, still **** nice CPU chips.
Your case, is an excellent choice. I have the Xon-102 silver/blue version Excellent cooling in it and lots of room. The PSU they give you with it is weak but it will support lower end systems easy enough with some extra connectors that the boxes will give you.
If I were you and I was a moderate gamer just looking for a cheap build I would get:
ASUS M2N-E -$93
EVGA 7600GT $130
Wintec 1GB(2x512) -$100
Wintec is known to be good stable memory for what its rated. I have always known wintec to be trusted, it's just not the overclock enthusist's brand. This RAM was stated to run max 430 FSB around meaning It should go fine with the X2. Or if you wanted you still could go with XMS since i'm sure that will suit your every need and more.