pcpartpicker.com mate. It's always updated & shows you a list of compatible parts, so you know whether any of your components will cause an issue.
This is my pc.
https://de.pcpartpicker.com/user/AFRLme/saved/j3znTW ignore the warning. It's just about possibly having to update bios for some shite or other. All of the components were carefully selected over time & with help from other people I asked.
My main issue with branded pc is that you end up having to pay more for one with good parts. You are essentially chucking more money at the brand, whereas you can potentially build a much better pc for the same price.
As for dust & heat. I have a decent liquid cooler, but I should have probably saved up & bought one with a larger radiator, but they were almost double the price of what I paid for a decent one. The cheapest corsair double 120 fan ones were about €30 or so more expensive. I clean the dust out every so often with a brush & I blow it out with a mini airbrush compressor too. I have decent anti-dust filters on my case, but it still manages to seep its way in somehow.