Any suggestions? shopping around this weekend.
What's
wrong with your 4-year old iPhone?
Apple's software support windows are far longer than 4 years. Is it on the latest iOS and still getting updates? If so, there's no reason to replace it.
Is the battery life suffering after 4 years? Check battery health, and if it's below 80% or so, replace the battery. They're not hard to do, or local shops will do it affordably enough if you don't have and won't develop the skills.
The cheapest option is to not replace it, and fix what's wrong, if it's having problems.