Everybody knows you need 2 saws

. You'll eventually need to get the first one out of a jam. Don't forget the wedges and safety gear. I wear chaps and a forestry helmet. Guys around here like to laugh about it but if you ever had a dead limb fall out of a tree while cutting it you'll be glad you have the helmet. Plus it keeps saw chips out of my face and it has ear pro.
I heat solely with wood and maintain my property, both my sisters' property, my parents' property, and do a little milling for personal use. Stihls are good saws but I don't have any experience with them. I have 5 Husky pro saws 268xp, 372xp, 395xp, 550xp, 572xp, 1 Husky 350, an Echo CS590 (which is a pro saw I believe?) and a small top handle saw for trimming. As a single saw for homeowner use, for the money, I'd go with the CS590. Learn how to use and maintain it, and when you go to get your second saw you'll know what you like/don't like about it. You can always size up if you need to and use the CS590 as a secondary.
I see advice of longer bars. Which is fine, and I'm no expert, but if you're not familiar running saws in my opinion I'd stick to a 20" bar, a longer bar is just more bar to get pinched, stuck in dirt, hit rocks, and more chain to file.
Learn how to mix fuel, learn to tune your carb (if it's not electronic), learn HOW and WHEN to file the chain (teeth and rakers), learn safe felling practices, and learn the correct way to cut blown down trees, a lot of people don't realize there's a lot of tension in them. Stay away from that rootball when it lets go. Check out arboristsite it's a good site with a lot of info you can learn from. Good luck and stay safe bud!