I bought a Dell XPS 435T (Intel Core i7-920 Processor - 8MB L3 Cache) about three and a half years ago. One of the fans has been getting progressively noisier for the last few months, making a growling sound. I took it in to get serviced. The tech told me the noise was from the fan on the video card and that it should be replaced. Radeon doesn't make this particular video card anymore (1024 MB ATI Radeon HD 4870 GDDR5). What would a comparable replacement card be that would work with my motherboard? Any help is much appreciated, and let me know if you need any additional specs on my system. Thanks for your time.