The worst computer to buy is consumer grade from box stores. Life expectancy a little over 3 years. A couple of months beyond the warranty. I've had this happen to me too many times. Buy .$10 cents on the dollar corporate return refurbs.
It's a good way to go for best bang for the buck.
Too many puters from Best Buy, etc are all but unusable due to engineering quirks. For instance touchpads with no buttons that require a special driver only available for one OS/version. A keyboard with "HOME" or other key accessible only by using the "FN" key. Failureware components used because they are cheap enough to put into a $250 laptop. Poor tactiles and ergonomics. Short lifespan parts. Nonstandard graphics specs.
A refurb used for months or years in a business environment will be a better grade of hardware all around. As an example, say that One Shell Square replaces every user laptop in the entire building just to keep up with the latest iteration of WinDOHs, and they return 3k desktops that were maybe not bleeding edge, but definitely up to date powerful machines when they were delivered two years ago. And now in order to keep a competitively equipped workforce they want to update/upgrade to the current state of the art in office computers. Shell gets a nice tradein discount from Dell. (or whoever) What's to refurb? New fans, new HD or SSD, wipe off the case, system restore, box em up. Ready to ship, for $300 instead of $1200. Good enough specs for all but the more demanding users. Especially if you are gonna run W7 (which I don't recommend due to security issues only) or Linux (which of course I do recommend for most users). For value, you will have a hard time beating a mass trade-in refurb from a well regarded maker. The new box selling for the same price might have a slightly faster processor and a more recent OEM install of WinDOHs but that's it. Crappy cheap budget hardware more suited to writing grocery lists or filling out a 1040a than serious computing, even trading/charting.
If you GOT to have new, skip the budget stuff. You will have better usability and reliability with office grade equipment. Now yeah we talk about RPi and other single board computers but I am talking about seriously capable machines here. The super cheap box that comes with the cheesy keyboard and herky jerky mouse and crappy monitor for a day or two's wages is not a good buy when you need it to make a living trading or whatever. Perfectly okay for Granny in the nursing home to check her email on. Not for business, hobby, or even gambling. Your trading definitely falls under at least one of thsoe categories, I am sure.