Personally, I think this is way over analyzed. For the things you want to do, and with the computers out today, there isn't one made in the last 10 years that can't do all you want from it.
I'd just look for a cheap Windows system (better file organization and cheaper) with:
An SD card slot (USB card readers are also an option)
A DVD Burner
WiFi if you have Wireless internet at home.
USB ports (pretty much a given)
The rest of the stuff isn't worth considering for what you want it to do. a 500g hard drive will hold something like 100,000 photos. If you get to that point, you'll want a totally different system anyway.
Stay cheap and light and portable is my opinion. By the time you learn how to use it to its capabilities, it'll be outdated anyway. Start small and stay cheap.
A desktop system with a full keyboard, mousepad, monitor, power strip, speakers, then a desk to put it all on…? Just not sure that's the route you'd want to take at this point. Especially if you're used to the mobility of an iPad. I'd go full sized laptop.