When you first start researching what you need for PC configuration and pricing in your PC, start at the end. By that I mean that one should consider their finished product, whether it is a simple letter, complex spread sheets, editing photos, creating graphical content such as a logo or even blue prints for construction. The question is, "What do I ultimately want to do with this new PC"?
For some users, the manufacturer will recommend PC configuration and pricing that is a catch-all and will work fine because all the want to do is balance the home budget and write letters. For other users with a need to produce computer process intensive work, one will need to start to research questions. Questions such as; How much DRAM do I need? What kind of DRAM do I need? How fast of a clock speed on my CPU do I need? What kind of graphics card, etc.?
In addition to this, every user should consider the future. One may start out just writing letters but in a year or so, you may want to create some art or get into a profession that will require more horsepower. So then, we begin to look at upgradability on the PC you are about to purchase.
When considering a PC purchase, the first look at the machine should be with consideration of it's proprietary nature. The question is; Is it proprietary or isn't it? In other words, if you need to upgrade your graphics capability, can you go to the store and buy a graphics card and plug it in? If not, your stuck with the manufacturer of your PC and stuck with whatever price they want to charge you. The good news there is that your shopping time will be drastically reduced. The bad news is, you are probably going to pay through the nose for the upgrade. Bottom line: Non-propriety is gold for you.
Considering your current requirements, the best place to start is to take a look at the "system requirements" listed with the software you want to run. Then, buy the upgrades available for the machine to the best of your budget constraints. You are better off going this way rather than upgrading later because the manufacturer will most likely have better upgrade prices at the time of your initial purchase. Now, I'm sure that you already know that computer technology changes faster than the time it takes to change your socks. So, no matter what your initial purchase is, you will eventually have to replace it. The combination of your initial purchase configuration and possible subsequent upgrades determines when that replacement will happen. But it will happen.
Next, we get into the technology itself. The most important considerations are the CPU speed, quantity and type of DRAM, the amount of storage (hard disk drive space) you will need, the motherboard BUS (I'll explain) and graphics capability. Other considerations are important, but not as important as these four considerations. The reason is simply for your current and future output.