The PSU looks like overkill but it can't hurt.
Personally I would skimp on the PSU and case and get an E6600 CPU, but huge PSU's are fashionable.... as are sound cards and cases

Normally, mainboards come with a cable bundle, why the secure cable? I just ripped a WD 250gb connector to pieces and wrecked a new harddrive with a secure cable that didn't release correctly when I tried to remove it, I didn't use much force either, so be careful.
You do realise that the E6300 is a 1.8ghz cpu and is not fast unless well overclocked right? That system should overclock very nicely, as the core components are all overclock compatible, ie, it's an overclocking rig...... for Mum? Or really for you ? ;)

Mainboard: Asus P5K-Premium, CPU=Intel E6850 @ x8x450fsb 3.6ghz, RAM: 4gb PC8500 Team Dark, Video: NV8800GT, HDD: 2x1Tb Samsung F3 RAID-0 + 1Tb F3, PSU: Antec 550 Basiq, OS: Win7x64, Display: 24&