you can get about 10% more performance (in 3dmark) by getting that 5770 and almost double the framerates in some games
http://www.tomshardware.com/charts/gaming-graphics-cards-charts-2009-high-quality-update-3/compare,1697.html?prod[3251]=on&prod[3231]=on&prod[3293]=on
The switches in a mouse (where you click) are only rated for so many clicks. They're not designed for a lifetime of clicking. I've worn out a mouse's left click button about every 2 or so years using logitech mice (mx300, mx310, g3). Doesn't your G5 have a warranty?