I hear a lot of people saying to buy the Antec 900 casing. I own one, but you have to think it through since its not suited for everyone.
+ looks good
+ Front panel connections at a convenient place(Top, tilted a bit forward)
+ reserved space on top for your nav, mobile phone, PDA etc.
+ cooling
+ Scythe Mugen Infinity fits(but side panel fan not anymore)
+ Drive bay modules (3*5.25" bays in a removable bracket, you get 2 brackets)
- Sucks in dust like a vacuum cleaner. The front panel where I have 2 sharkoon fans is filled with dust within 2 weeks.
- Cable management non-existant. I have a modular power supply, but still inside the case it's a mess, and I have tried everything to get it done right. I also use rounded IDE cables.
- The supplied fans RPM can only be changed by a tiny switch thats connected to the fan inside the case.
- No fan RPM readout, connector is molex
- Fan LED's can't be turned off
- The motherboard backplate cannot be taken out, so mounting a mobo is a hassle.
And like others said, get a budget and go for mainstream products with mainstream prices. You'll get ~85% of the performance at ~50% of the costs. What might be important (at least for me) is power consumption. But they can be misleading, for instance for processors. Intels maximum TDP is more of an average, AMD's TDP is the absolute maximum the CPU could ever use in any circumstance, which in real world applications will mostly never be reached.
GPU's use in the whereabouts of 90-110 watts, HD3850,HD3870 as an example. Offcourse high end uses more.
Also do not exaggerate on PSU wattage rating, 450W is more then enough, as long as its an A-brand. I own a BeQuiet! Darkpower P7 pro 430W, which might be handy if you still want to buy that antec 900 casing. It can control your case fans supplied with the Antec 900, it has fan RPM readout of its internal fan and is modular. The fans spin faster as PSU load increases, mine have never spinned faster, always at lowest speed. That gives you an indication of power consumption since I own a typical mainstream system. It consists of am AMD 5600+ X2(TDP=89W), HD3870, 2*2GB Ram, 2 HD's, DVD burner.
My ATI experience (own a 9800pro and a HD3870). ATI makes hardware wise the most competitive and well rounded cards at an unsurpassed price. Only to have it ruined by the drivers
. They work for most of the time, but things like getting a 3360*1050 resolution to work in span mode is a step too far it seems. The drivers don't support it, the hardware does. It's all these tiny things that ruin it a bit. Don't know about nVidia, but from what I read if you want cutting edge you need to find the right driver, which isn't necessarely the latest it seems. So seems frustating at times too.
Also go for DDR2 PC6400, or PC8500 if price is almost the same, DDR3 is too expensive and by the time it's just as affordable as DDR2 you'll probably be buying a new rig anyway.