This question troubles a lot of people because it deals with the nuts and bolts of your network operations and also demands investing a hefty amount of money.
It is true that servers cost a lot. The question is if they cost more than the downtime caused by an aging server. Certainly not. Imagine the loss of precious data and potentially the loss of clients when the server goes down repeatedly despite multiple troubleshooting attempts. We are having a hard time imagining such a dreadful situation and surely you are too.