We must assume this is for gaming so here are my thoughts/opinions (others will give their own):
1. Drop the CPU and instead get the Athlon 3200+ for $135.00 at NewEgg. Or consider the 3700+ San Diego, an Opteran 144 or 146, or an X2 3800 + Manchester. Less money and all are great ocers including the 3200+ venice.
2. Unless you are going to run SLi and your going to buy a second video card, don't get a SLi motherboard because it will be a waste of money. Besides, there is great debate about the cost to performance ratio with SLi and that is why I didn't pursue it.
Suggestion: EPoX 9NPA+Ultra. Great motherboard that is rock stable at stock settings and a good satble overclocker. Many people have this board including yours truly in my new build. By the way you can get this for under $100.00.
3. I have a Thermaltake and I love it. How many case fans come with that model? Mine comes with 2 120 mm fans and it does the job, so you might not need to spend the money on a case fan unless you are planning to overclock.
4. Power Supply - Antec TruePower 2.0 550 W or Fortran 480W or an Enermax. You can get these for right around $100.
5. Video Card - Look at the x1800 GTO ATI or the Nvidia 7800 series.
6. Monitor - believe it or not this will be one of your most expensive items. For a good one from the 17" to 19" range get ready to spend around $300, plus or minus by about $30, for a Samsung or ViewSonic LCD deal. NewEgg has some great deals going on right now along with the Athlon 64 3200+ cpu for $135.00. If you are a gamer you don't really want any monitor whose response time is higher than 8ms.
7. Keyboard and mouse - go to your local Staples, etc. and pick it out. Be aware that Logitech Optical mice have issues with Windows 32 system and give you the dreaded Blue Screen of Death with a Stop Error. I speak from personal experience because I have one and I've gotten these screens. The Mouseware drivers 8.0xxx through 9.1 are the cause. Perhaps the latest opticals have better drivers. The MX310 still comes with the 2003 9.1 driver and it is a pain beacuse Logitech has yet to change the driver. Why they still ship it out in shiny new boxes knowing this issue is irreponsible.
* If you shop smartly and wisely and make decisive decisions you can build a great system for $1,500, I know because I have done it.