I think you need to clarify what you are looking to do here. Are you looking to day-trade, run your own HFT shop, do fundamental analysis, or something else? I'll address each in order.
High Frequency Trading (HFT): You'd be going up against the big boys like Knight(now Virtu), Cantor, Citadel, and Jane st. trying to squeeze fractions of a penny out of stock transactions many times per second or to arb quotes across exchanges via software you write. What do you need there? More than you can afford: Top of the line server equipment, colocation with the exchange's datacenter etc. (because the speed of light just isn't fast enough) A fun fact is that the very first high-speed internet was built by HFT firms. When you're trying to arbitrage commodity prices between the NYMEX in NYC and CBOE in ChiTown it matters if your fiber-optic cable goes through Akron or circles around it.
Day Trading: Basically betting that a company like Coke will go up in the next six hours. Basically any old toaster and a DSL or better internet connection will do. I don't know what sort of software you'll be using, but it's likely to be a spreadsheet to track positions and P/L along with some basic technical analysis software. I've got separate opinions about an average person's ability to make money doing this, or the value of technical analysis overall, but I'm going to leave them out of this discussion.
Fundamental/Macro/Quant Analysis: Researching individual companies and forming valuation expectations for them, and buying and holding to see if you're right, OR studying macroeconomic signals and how they affect company/sector/factor performance, etc. OR studying how fundamental company characteristics affect return. I'd say that what I do mostly slots somewhere in here. My load-out includes Bloomberg, FactSet and Morningstar Direct and I will frequently be working with excels that are 10s of MB large.(always turn auto-refresh off for those btw.) My WFH setup is an i5 4670 quad at a bit under 4ghz and 32GB RAM. The RAM is really needed here, and I'd suggest some sort of SSD, although it's unlikely to be a limiting factor. The graphics card just needs to be fast enough to drive the monitors, honestly unless the mouse movement at 30hz bugs you it's fine for what you'll be doing. Also: a huge monolithic extreme HD monitor doesn't play nice with a lot of these programs, particularly Bloomberg. I learned this the hard way, since I never designed this as a workstation. A bunch of cheap ~24" 1080p monitors would be ideal. (at work most people have at least a 4=pack, with 6 being the normal load-out.