First Build - component questions

My goal is to build a fast and quiet system.

Components
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Antec Sonata III Black 0.8mm cold rolled steel ATX Mid Tower Computer Case 500W Power Supply $149.95
ASUS P5B Deluxe LGA 775 Intel P965 Express ATX Intel Motherboard $176.99
EVGA 320-P2-N811-AR GeForce 8800GTS 320MB GDDR3 PCI Express x16 HDCP Video Card $279.99
Antec True Power Trio TP3-550 ATX12V 550W Power Supply with Three 12V Rails $99.99
Intel Core 2 Quad Q6600 Kentsfield 2.4GHz LGA 775 Processor Model BX80562Q6600 $309.99
2 CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) $230.00
2 Western Digital Caviar SE16 WD5000AAKS 500GB 7200 RPM SATA 3.0Gb/s Hard Drive $219.98
Subtotal: $1,466.89

Here are my questions:
- Is there anything that I miss from the component list? I don't have fan and heat sink. Can
you recommend a good heat sink for this system.
- Is the 500W PSU enough for the system?
- Will the motherboard and/or Windows XP recognize all of the 4GB memory? I am planning
to use the system for video editing.
- Is there a better component (MB, GPU, case, or PSU) that you would recommend? I am going with
Q6600. Everything else is opened for me.

Thanks in advance for your feedback!