I think that Luca is right about your noisy card being more powerful than anything you can replace it with in your price range. However, there is more than one way to skin the cat, says an old saying. Or there is more than one way to quiet your computer. Read on:
All of the ASUS 8800 cards that I have seen doing searches today have a 2-pin connector for their fans. Does yours? If it does, and if you are happy with the graphics performance of your 8800, and if you have the knowledge, then you can simply control the fan speed yourself. And it can cost almost nothing, not even $50 US if you want.
Here is a link to the Zalman Fan Mate controller, it is only 5.95 USD, and may do the job for you. Note that the little controller part goes wherever you can fit it inside the computer. You do not have access to it from the front panel.http://www.frozencpu.com/products/984/bus-08/Zalman_FAN_MATE_2_Variable_Speed_Fan_Controller_FanMate-2.html?tl=g47c17
If you would like to be able to control the fan on your 8800 from the front panel, and if you have a 5.25" bay available to stick the controller in, then there are several possibilities in your price range. And almost all of them can control more than one fan, so you can have control over the other fans in your system too.
If you have a lot of fans to control. http://www.frozencpu.com/products/13401/bus-263/Scythe_Kaze_Q-12_525_Bay_12_Channel_Fan_Controller_-_Silver_KQ02-SL.html?tl=g47c17s286http://www.frozencpu.com/products/6135/bus-108/Zalman_ZM-MFC1_Plus_Multi_Fan_Controller_-_Silver.html?tl=g47c17s286
If you would like to add card reading/and additional USB 2.0 and SATA connectors http://www.frozencpu.com/products/13876/bus-274/Akasa_525_Bay_All-In-One_Fan_Controller_Card_Reader_Multi_Port_Panel_-_Black_AK-ALL01-BK.html?tl=g47c17s286
Here is a link to the fan controllers at Frozen CPU, this is all of them, 5.25" bay, 3.5" bay, etc.:http://www.frozencpu.com/cat/l2/g47/c17/list/p1/Fan_Accessories-Fan_Controllers.html
Note that you may need a cable to adapt your 2-pin fan to the 3-pin connectors on the controllers. But if the fan's connector fits the right way, you won't. You may also need some kind of extension so that the fan cable can reach the controller, some don't come with cables. To get answers to these questions, and even more info, you can contact the guys at Frozen CPU. I have found them to be reliable, honest and knowledgeable. Contact info is lower left side of any page. If you email them, use the email for order and website support.
You will need software to monitor the temperature of your 8800 if you choose a controller that does not have a temperature readout and thermal probes. Such software should be readily available free, I think.
Also, if you browse the whole list of fan controllers at FrozenCPU, I suggest that you stay away from the ones with the touch screens. A touch screen that works well and is reliable simply can not be made in these price ranges.
If you have any more questions, please post them and we'll be glad to do what we can to help.