we are looking into updating our 25 (or more) year old SlantFin Gaxaxy that has certainly seen better days.
I've been recommended SlantFin Bobcat, Burnham 206, System 2000, & Buderus amongst others.
We have also been recommended an indirect DHW, by HeatFlo, Amtrol, Heat Transfer and others.

At thsi level are they all pretty much the same quality and it's a choice between who you like and price, or is there more I need to look into?

We will also be making our 1 zone into 3.