When looking for a chair you first need to know your measurements. Height, width and depth of the seat are 1st priority followed by back height and arm height. Your weight is important when assessing the different foam densities and even fabric texture can be relevant. If you are going for a seat that "moves" you need to be aware there are different actions available that can make a significant difference. After getting the right size, flexibility is key. Something like a waterfall back where the cushions are accessible to change the stuffing is really important, multi way actions will work not just for today but for next years problems as well.
Car seats can be brilliant, Volvo's are one of the best. Retain as much of the variable actions as possible - it doesn't matter what colour it is or what it looks like, if it works for you !
You need to sit in a chair for at least a few hours, preferably a few days or a week before deciding. Remember that over time the chair will adjust to you and you will adjust to the chair making everything very comfy. If you get the sizes and shapes wrong those adjustments to the chair will make you worse.
All I do is chairs for the disabled, so if you need more info just pm
Clive