Just keep an eye on the power usage, depending on how expensive electricity is in your area. I live in California which has very expensive electricity, and buying newer, more power efficient hardware works out cheaper than 10+ year old Xeons over the long run, even if you get the Xeon system for free.
You can do quite a bit with 4GB RAM. A lot of people use VPSes with 4GB (or less) RAM for web hosting, small database servers, backups, etc. Big providers like DigitalOcean tend to have 1GB RAM in their lowest plans.