Yes a fair amount. The A64s general are faster clock-for-clock than an equivalent XP processor due to several enhancements, plus with a 144 which can likely be overclocked to 2.6ghz is equivalent to like a A64 4400+ (I'm just estimating here, since a 1MB L2 San Diego at 2.2ghz is rated for 3700+) which is quite an upgrade over your fastest 2800+. And even more so that HL2 is more CPU bound than other heavy GPU bound games like FEAR.
For a huge performance increase, pick up one of these 144s or similar A64 as well as a 7900GT.
edit: And damn what the hell. I paid $240 for my 146 and it isn't even completely stable at 2.8ghz with an enormous 1.55 V. My load temps are 50-51!! Damn everyone else gets so lucky and I never get good overclocking chips. I'm using the stock AMD heatpipe too, so I should be getting thermals in the area of the other stock heatpipe and XP-90 users... but I'm pretty hot. I have my side panel off too for cooling which with my tests is a little better since I don't have good fans and airflow.
For a huge performance increase, pick up one of these 144s or similar A64 as well as a 7900GT.
edit: And damn what the hell. I paid $240 for my 146 and it isn't even completely stable at 2.8ghz with an enormous 1.55 V. My load temps are 50-51!! Damn everyone else gets so lucky and I never get good overclocking chips. I'm using the stock AMD heatpipe too, so I should be getting thermals in the area of the other stock heatpipe and XP-90 users... but I'm pretty hot. I have my side panel off too for cooling which with my tests is a little better since I don't have good fans and airflow.