[Fyron]

Anyone that tells you that it is not necessary to have proper case cooling (at least one intake fan on the front and one on the back) should be summarily ignored. You especially want an intake fan blowing air over your hdd bays... Sure, a core 2 duo might put out a bit less heat than a Pentium 4 Extreme or whatever, but it still makes a lot of heat under load. So does the RAM, motherboard, video card, hdds, etc. Nothing but CPUs has really had much engineering done towards reducing energy usage and heat output. You want some airflow going through the case. You do not need to create a wind tunnel, however. Slower, quiet fans are good for case fans (many people even voltage-mod their case fans down to 5 or even 3.3 volts, for even less noise output). Panasonic makes some good case fans (Panaflo), for example. Most motherboards can control fan speeds based on thermal sensor readings, and slow them down when less heat is being generated. You could also get fans with built-in switches to control speed, or one of those front-mount fan control panels.

Quad core is still snake oil for 99% of people. It is not worth the extra investment. Any worthwhile motherboard you get will support both dual and quad core CPUs. By the time quad core is really necessary, you will be able to get a replacement CPU for less than the difference in cost between the dual core and quad core you would buy today. Die shrinks and process improvements make silicon get real cheap, real fast. Then you've got inflation working to your advantage; just look at how cheaply you can get 3-4 year old CPUs today. It never makes any sense to buy bleeding edge technology. CPUs and video cards are particularly bad, with massive markups on new architectures for the first 6-12 months.

Standalone HD-DVD players do not cost anywhere near that much money... and by the time you would consider getting one for your PC anyways (after affordable burners come out), they will cost $30-50 US.