New Dutch system build

Arctic Cooling Freezer 7 Pro (Socket 775)
€ 14,60

Asus P5Q
€ 88,45

Club3D CGAX-4872DD
€ 199,68

Cooler Master Centurion 590 Zwart
€ 53,70

Intel Core 2 Duo E8400
127 euro

Logitech Media Keyboard
€ 8,79

Logitech MX518 Optical Mouse (USB)
€ 23,80

OCZ Gold OCZ2G8004GK 4GB (2x 2GB) DDR2
€ 65,57

Samsung SH-S223F
€ 16,56

Samsung Spinpoint F1 HD753LJ, 750GB
€ 72,-

Samsung Syncmaster 223BW
€ 198,-

Zalman ZM-F3 (120mm, 3p, 20 dB) X2
€ 4,75 (9,50 total)
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this is the system i'm planning to build. prices are in euro's. i already have an BeQuiet Straightpower 650 watt. so no PSU needed.
800-900 is my maximum price range. i also plan on overclocking my proccesor. it's my first homebuilt system, and my first overclock
 
i now run a Dell E520 with: (just to tell how much this sucks )
AMD athlon X2 4600+
Passive Dell X1300 pro
2GB 400mhz (200mhz dual channel) samsung valueram
Dell mobo (?)
No cpu cooler (just a small alluminium block)
305 watt PSU (dell)
1 120mm fan (unknown brand)
 
my case is also mirrored, everything is in the wrong place, and because of that i can't replace videocard with bigger one (no dual slot, and 3850 didn't fit. and the other problem is no pushpins so no cooler upgrade.
 
does anyone have any advice on this build, my main questions are

regarding my videocard is the 4850 not far more bang for buck (45% cheaper). it prob. plays all games.

Is the E7200 a better processor at this budget.... or the Q6600. Q9XXX is all 240+ so those are out of the question

and...
at 72 euro's, the 750GB (32Mb cache) spinpoint F1 is better than:
Samsung spinpoint F1 640 Gb (16 Mb cache).
however, with the latter being priced at 56 euro, does the performance gain justifie the price difference.
Cost per GB:
640 gb= 0.0875 euro
750 gb= 0,096 euro

prices here in holland are:
 
8800GT= 100 euro
4850= 135 euro
4870= 202 euro
9800GTX= 180 euro
9600 GT= 79 euro
 
and for proc's
 
E8400= 127 euro
Q6600= 138 euro
E8500=140 euro
E7200= 86 euro