How should I DOWNgrade my gamingish system?

[coldReactive]

I want to know what I should downgrade in my system to do the following:

1. To get at least some money back.
2. To at least be able to play flash (IE: Homestar Runner) on Linux. This means I need at least 2.4 GHz Single-Core.
3. So that my computer won't take as much power and use less fans.

Currently, this is my setup:

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* GIGABYTE EP43-UD3L Motherboard (No Integrated Video)
* Front, Side (Processor) and Back Fans
* Intel Core 2 Duo (E8400) @ 3.00 GHz for both cores
* 6125 MB RAM (3 slots taken out of four)
* Windows XP Pro x64 Disk Included, but not installed (Activated Twice)
* 500 GB ATA ST3500418AS
* DVD-RAM Drive (DVD/CD Burner) LG Model GH22LS50 (Without Bluebirds)
* nVidia GeForce GTS 250 (1 GB) Video Card (HDMI and VGA tested)
* Realtek RTL8111/8168B Gigabit Ethernet Controller (Integrated)
* Sleep Button On Front
* Headphone/Mic Jack on Front (I need these)
* AGI 550W ATX12V Power Supply
* 4 USB On Front, 8 In Back
* PS/2 Ports for Keyboard and Mouse
* SPDIF Out on Back
* Intel [HDA Intel], device 0: ALC888 Analog [ALC888 Analog] (Integrated)
* Intel [HDA Intel], device 1: ALC888 Digital [ALC888 Digital] (Integrated)

Please list things I can downgrade and what I can downgrade them to. So I can bring the list to my computer store (Not Geek Squad ) and they can look it over.

[NejinOniwa]

The Processor, mainly, is ridiculously overpowered - it is also the main source of heat on the device, together with the graphics card - which is possibly even MORE overpowered in this case. I'd recommend you to downgrade to some halfway-shitty Radeon budget card for graphics (for example, the Radeon HD 4370 is a good shit-card), to start - I'm unsure how much it's worth to swap the processor, and besides, as long as you keep it down in usage and have a good fan setup, it won't be very loud either. The PSU doesn't need all that much juice either; I'd say 450 or 400 watts is a good target there.
Ironically, the best way to get a silent-running computer is to have fuckass-overpowered fans on it; if it weren't for my graphics card (the fans on the Radeon HD 4870 are so damn loud it's stupid) my system would be silent as the hill (lol), and I upgraded my fans this summer. Zalman and ArcticCooling units are recommended - I personally use a bigass Zalman fan for my processor (and I mean bigass, it's almost too big for the case ; ), and since it comes with a fan tuner, I can spin it down to the minimum speed all the time - even while gaming! - and have almost dead silence from my unit.
However, removing fans is redundant (unless you're really desperate) since it creates more trouble than it resolves; remove a fan, and the rest of the fannery will have to work so much harder to keep the cool (particularly the CPU fan, which will have its load increased by a fuckton) by themselves that you actually lose whatever bonus you gained by removing the fan in the first place. If you have a retail fan on your cpu (the one that came with it in the box, that is) I highly recommend changing it to something better and more efficient.
Aside from that, there's little else to do that's price-efficient; you could spend hundreds of dollars on little things, but that's not exactly what we're looking for here, is it. -w-;