I am sort of going down this route, starting with a new Star Trek Pro, and am currently keeping a semi-serious eye out for a local F-14 Tomcat to complement it. Buying the ST used would keep that combo under 6700.
If I were to look for two games of closer to equal value, I have played and enjoyed No Fear and Fish Tales right next to each other at a bar in Arizona. Those are both in the 3K+ range.
Of course you have to do you, but I think it's certainly possible to have a combo you would enjoy for that budget.