@ace4059 : Now that you've picked a saw I'd suggest grabbing at least 2 different sized bars for it, one being what you're comfortable with and one that's 4" longer, and perhaps one 4" longer than that. The bar weight helps it cut faster while you're mostly relaxing, plus the additional reach means not bending over so much. When you've a really big tree you'll have the 400 for the smaller parts and "the big bar" for the 500, which is really, really nice at that point not having to lean over the trunk and wrap a cut with a smaller bar; in that case "the big bar" is faster
and less work.
The Husqvarna X-Cut chain is really fast though if you look at it you'll see
a 7/16" file isn't going to restore the cutter profile (and you need more than a 2-in-1 sharpener), so since you're using a 2-in-1 maybe stick with STIHL RS or RSK (full chisel) chain for clean wood and RM (semi chisel) for dirty wood. After trying various chains
I'm going to get Carlton chipper chain for really dirty wood (no chisel), it's "slower" at first though quickly surpasses other chains in dirty wood because it resists dulling.
Congrats on your decision, I think you'll be really happy with it.