I rarely upgrade. I'll always try modifying something. If you don't like what you've done, put the old parts back, try something else, or forget it.
This is not for most people. It takes a few years to learn what parts of a circuit to change. Most manufacturers spend a lot of time voicing their equipment, so you'll have to too.
It's cheaper than buying something new every year. You'll end up with something that sounds a little bit better. None of my stuff is new. I don't care about warranty or resale.