If your main complaint about your R300 is the noise, I suggest you aim for something FANLESS. There are some nice R700 fanless cards available cheap. There are also evergreen/northern_islands fanless cards available that should work fine, but the downside is that HDMI audio hasn't been implemented on them yet (if this is a consideration for you...).
SAPPHIRE Ultimate HD 6670 (Northern Islands)
SAPPHIRE Ultimate HD 5670 (Evergreen)
SAPPHIRE Ultimate HD 4670 (R700 -- HDMI audio)