To be honest, you'll most likely want to upgrade your entire system if you want to play all the latest titles maxed out. Any GPU that's really a 'match' for your system will not be able to max out the most recent titles, nor will it be really be suitable for gaming. But that's just my opinion, so someone correct me if I'm wrong.
Your cpu isnt good enough to max out the latest games, no matter what gpu you have. To max out the latest games you need a decent, modern quad core cpu, a GTX570, or AMD HD6970 class GPU , and it will take a quality 600 watt power supply to power it.
(second post I've followed you on mocchan, just thought that was an odd coincidence)