Below is a link to a helpful tool for deciding whether to upgrade or not. Keep in mind too that 410a has been phased out and coming across a new 410a unit is a bit difficult. It's more likely you'll end up with R32 or 454b unit which, I think, requires a sensor in the furnace or air handler. At a minimum your system is rated at 10 SEER if it's 25 years old.
https://www.seerenergysavings.com/