yahoo sbc dsl is the provider and my modem is over 5 years old. id imagine modem technology has progressed quite a bit since then
Well... yes and no.
Yes, technology advances continously, so a newer dsl/cable modem might be quicker by virtue of a more powerful circuits, more efficient or easier to manage and configure, especially if you use wireless.
But, if there is something regarding computers that has stayed fairly constant, that is networking. Shure, there have been fairly big jumps from time to time, but if you're already using DSL, you're doing ok. Most older modems can go up to 4 or 8 Mb/s, even if you were being sold only a .512 Mb/s contract.
I'm not saying you shouln't buy one, I'd recommend to ask your service provider what upgrade/replacement equipment they offer, but getting a new modem might not help as much as you think. Making shure your phone line is properly installed and has no line noise would be a good step; if it does have some noise and you eliminate it you'll probably get a nice jump in performance.
Lastly a lot of games' "network speed" bars measure latency. Latency in networking is the delay that a piece of information suffers because of making it's way (jumping) from one network to another to its final destination. Without going into a lot of technobabble, latency is influenced by your internet providers network design, and you can't really do anything about it, unless you switch providers and hope they are better.
I hope I didn't make things confusing. Cheers!