The thing you have to keep in mind is what way you're going to handle graphics. Whether you're using your on board graphics in your CPU or a separate GPU, the thing which limits your ability for higher resolutions is how much ram and how much the cache can handle at a time. I was not aware of the shadow issue as MrV said above, so that's another consideration.
But skins/textures are what take up so much memory, not the models or the scripting, etc.
For CPU you have to give it sufficient system RAM, and in addition to caching you have to keep an eye on system resources a little more closely. This is a simpler way to set it up, though. Usually not a huge concern unless you have other applications running in the background. Make sure you have better cooling than your stock fan in any case.
For GPU an average amount of Vram is 2 to 4GB, 6GB is beginning to get large, and the upper levels are 12GB (so far as I know) for Titans and Teslas (these are professional, not something a gamer or hobbyist will buy).
Also the frequency clock is an important factor as well. For gaming you ideally want one optimized for it (performance).
There may be higher end cards as you will note, but these are more meant for workstation and production and not necessarily performance. They could play games but may not be optimized to handle them at their best settings. A production graphics card's architecture (circuit layout) is meant to spend hours or even days on end rendering and calculating and shrugging off heat that would likely kill other cards. For my purposes I don't necessarily need a "balls-to-the-wall" card.
Obviously you want a PSU which can handle your whole system, a graphics card, and then some. Higher the quality, the better components it's made from and the longer it will last. Sure, more efficient too, but any SMPS (Switch Mode Power Supply) is designed to be equal to or over 90% efficient.
For sound...I have found a simple USB SoundBlaster soundcard with a good set of headphones or some compact speakers with at least some surround capability works well.
For peripherals...
Keyboard, I'm going to say go with Logitech mechanical as I have seen several disappointments by Razer. Corsair keyboards look like they fare nicely. There's that glove thing, though, and I don't know how well it'd work. Or if you want general purpose, something with ergonomics in mind. I have a Microsoft 4000 ergonomic I use on and off and it's pretty nice, if a bit large. Don't pay more than about $40-50.
Mouse? For MMO get one which is multi button (here at least Razer doesn't disappoint). For action based I'd otherwise recommend something with fast response like the G502 proteus core.
Monitor...frankly a mid range gaming level Asus will probably do fine for SWTOR. I'm not sure what game requires the refresh rate of a BenQ.
Obvbiously there's a ton more choices, I'm just mentioning what's commonly available that works.