The FT-817ND or any other low power rig including the Elecraft is a bad choice for first HF rig unless you plan to spend fruitless hours with your compromised antenna making very few, if any contacts on a normal day.
If you have $900 to spend on a brand new radio, buy a FT-450D. IF filtering, Roofing filter, internal ATU, 100w, HF+6m.
Problem here is....as he clearly states his living conditions a 100 watt rig is sure to create problems for him and his neighbors guaranteed. Even 50 watts is most likey going to do the job at reaking havoc. In some cases dependent on frequency range may exclude the issue, but sure the RFI is gonna screw with his rig, power supply, TV, radio etc....
Running QRP will be the safest for him both operating and keeping his neighbors clueless.
Don't let the nay Sayers tell you that QRP is not for the beginner ham. I started out running QRP and even though the solar cycle was much different then the QRP woes were still very much present. In fact if you look me up on YouTube I have many videos that prove all those nay Sayers that QRP is not gonna work under the worst conditions quite contradictory. Last 10 years have been the worst and still able to bust pile ups with 5 watts against guys running 1500 watts with yagis on 50ft towers.
All in the field with compromised antennas!
If you don't care about the 2m/70cm band and money's not an issue then the KX3 is the way to go hands down if it's gonna sit on your desk. If you plan on going on hikes and stuff the KX3 is the way too go, but the FT-817ND is for me because it's all bands I use rolled up in one. I've even contested with it and has it's lack of filter capability compared to the KX3 stop it and me from high contact numbers during a low weak solar cycle? HELL No!
That too I prove in my videos!
So if money is not an issue buy both. If you wanna see what a 100 watt radio is gonna do for you In your apartment that would be a good idea. Just crank it down to QRP if need too.
Just too many options and too many variables to consider unless you just dive into the radio of your choice. There's never an easy solution nor can anyone predict what's best for you.
Just buy a radio and see for yourself.
73 and good luck!