What specifically is the goal for your need to upgrade?
Increased gaming performance (what games)?
The problem is that system uses a proprietary motherboard and power supply, so certain upgrading will be limited.
Your system will only handle up to a AMD Ryzen7-2700 65w CPU but the only advantage is two more cores. Speed wise you wont see a difference as far as clock speed in games. They are within .2Mhz of each other. Only if you are heavily multi-tasking will it help much.
The manual is confusing as it claims up to 32GB ram, but it only states up to 8GB dimms and there are only two slots.
But Crucials Memory Finder states that it can handle up to 16GB dimms so I am confident you can go up to 32GB total. They guarantee their ram to work or your money back.
It takes 2400MHz DDR4. But if you only want to upgrade from 8 to 16, you should use CPUz to find the timings of your original stick and match that with another 8GB stick. This will help ensure compatibility and that it will run in dual channel.
The power supply you have is 400w small form factor and proprietary to the motherboard. You cant just buy any ol PSU and install it because the board doesn't have a standard power pin-out.
You can order a 500w PSU (L05757-800) through HP that will work if you are going to upgrade your video card to something that requires it, but note how much available space you have to install one in that case. You will want a blower style card if you do, so to exhaust the air out the back, not back inside the case. Those PSU's are a tad pricey.
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