make sure the package from your ISP helps with your games, most offer packages for gamers, which means their gaming traffic gets priority. Also when you moved from dial-up to broadband, i would assume they gave you a router to fit to your home PC, and that you are not using wireless for gaming.
Use a good Cat5e/6 LAN cable to connect your PC to the router, to get the fastest link possible to your device. then verify that your 1.5Mb package speed is working as best as possible by doing speed tests during the day and late at night, to test the traffic load and contention (sharing) ratio of your neighbourhood.
this will give you an indication on how good your link is in real-life tests. if you find your hitting 1Mb+ on the tests, you have a good link, any high latency issues, maybe caused by other factors, such as game server speed, ISP throttling etc......the causes can be numerous, and by trial and error, you can reduce the list. Also make sure your router has the latest firmware, visit the manufacturer's website.
