Antec Solo is a good, quiet case for ex. Not exspensive either.
Just replace the Antec tricool fan with a Nexus 120 mm (softmounted with elastic cords). Remove the honeycombed fan grille first, before you mount anything into the case. This will lower the noise further and improves the air flow. Also seal the vent in the rear of the case.
Just make sure you clean the case throughout after the cutting.
If you feel the need of an intake fan? Then a 92mm Nexus is a good choise.
As for videocard. Get a passive AGP Geforce 7600GS ( GIGABYTE GV-N76G256D-RH). Those are pretty cheap and decently powerful.
If you wanna keep the 9800Pro? Then replace the stock cooler with a Zalman VF900 CU instead. Fits all 9000 series cards except 9500 and 9600. Replacing the included thermal paste with Arctic Silver Ceramique, will lower the temp a couple of degrees more. At the lowest to mid setting, this vga cooler is very quiet and still cools very well. Very simple to mount. Comes with RAM sinks, that have thermal tape pre appied. Just clean the gpu and memory throughout with oil free Acetone or Isopropyl alchol, and a lint free cloth before mounting cooler / RAM sinks.
A good strategy, is to mount the RAM sinks first. Then letting the tape settle for a few hours, before you mount the Zalman cooler. Othervice you risk that the RAM sinks comes off easily.
http://www.zalman.co.kr/eng/product/vie ... 2&code=013
The Corsair HX 520, is said to be a silent psu. This is a modular powersupply, wich means, you just hook up the cables that you are using for the moment.
This will help you to reduce the cable clutter.
The HX 520 is 20 + 4 pin main power connector, so you will need one of these for your AMD motherboard.
http://www.newegg.com/Product/Product.a ... 6812145002
Heatsink. Scythe Ninja Plus with a 120mm Nexus, Or a Noctua NH-U12 for ex. Check motherboard compability at the manufacturers home first.
It's probably possible to run the Ninja without any fan at all. If you make a simple duct made out of cardboard ( preferably glossy), or plastic. And connect the duct to the rear exhaust fan of the Solo case.
A cheap but slightly noiser soloution, would be Arctic Cooling Freezer 64.
This will work with 99 % of the motherboard brands and models.
The Freezer will still cool better, and be noticeable more quiet than the stock fan / heatsink.
Any of those heatsinks, will fit into most cpu sockets of today.