Can I get more speed by just replacing a chip?
The easiest upgrade you can perform is adding more RAM memory. 64MB of RAM seems to be the price/performance sweet spot. You can also replace/upgrade your CPU to achieve even greater performance.
For more detailed information or to purchase these upgrades visit the sites at:
PNY Technologies - Memory upgrades
Evergreen Technologies - CPU upgrades
Kingston Technologies - Both memory and CPU upgrades
Crucial Technology - Memory upgrades