I think almost any decent desktop from a big name brand made in the last 5 years, with only a few mods such as SSD drive, plenty of RAM, and a good graphics card, will do you just fine. The trick is to keep the software from crippling the hardware. Something WinDOHs isn't very good at. If your brokerage offers or allows a trading platform that is available in a Linux version, you might find Debian, Mint, or Ubuntu to be very good for keeping your machine mean and lean, especially if you only use it for trading. You might want an entirely separate machine for web browsing etc. You will get nice fast boot times and a fast and responsive system that way, I am thinking.
When it comes to computing, we are usually our own worst enemy. Most virii (something we Linux users actually dont know much about LOL) are introduced into a system by stupid computing practices. Cookies can be inoccuous or even helpful but they are robbing your computing resources. "Advanced" web browsers combined with media and scripting intensive websites slow browsing down. Web based email... I don't use it, no. A good standalone email client (NOT OUTLOOK!) has a much lower presence on your puter. Gaming? Separate computer. Graphics/Video editing, capturing, viewing, transcoding? Ripping? Music? Sure. Do that stuff. On another computer. Keep your hard drive size reasonable. You don't want a 4TB drive to boot and run from, especially if it is crammed to the gills with multigigabyte files. A good quality 200GB SSD drive will make a big difference, especially if it stays less than half full. If you insist on running WinDOHs, every few months defrag your drive, and every year back it up, wipe it and do a full reinstall. I don't know maybe W10 is better about that than previous incarnations. And for petes sake, if you use WinDOHs, set your file manager to always show filename extensions so you don't click on "HotBabeOnHotBabe.mpg.exe" thinking it is a video you simply must see.