Don't get a Steambox, just build your own PC.
Depends on your budget really. Having and keeping up with a gaming PC will end up being tons more expensive than buying a console in the long run.
So if you want to stay cheap and have access to newer games for the next 8 or so years, buy an XBOne.
If you have money to burn every 3-5 years (maybe more if you don't mind using low settings after a while) for upgrading a gaming PC, get a gaming PC.
Sure, new games on PC usually do cost less. Shame that you have to wait a couple months before they are released on PC if they were console multiplats prior, which was the case with Grand Theft Auto V or Metal Gear Rising, not to look for examples too far. You have the argument of Steam Sales and other such promotions, but Xbox Live and PSN are quickly catching up to the "flash sale craze" and they're organizing their own regularily now. Not only that, but on PC most of your purchases will be digital while on consoles you can always trade one game disc for another at any time in any game store. Both solutions have qualities to them - PC has cheaper games, but consoles have the convenience. Consoles have much cheaper hardware that you don't have to upgrade once throughout the generation, PC's can be freely upgraded, but the upgrades often cost quite a bit, especially during generation shifts when your CPU socket just "doesn't cut it anymore" and your entire setup might as well be trashed because newer, better CPU's or memory just won't work with it. PC offers top quality gaming, but it comes at a price. It's getting more and more convenient and affordable, but it still hasn't reached "console-level" of convenience.Actually I would like to disagree.
Yes, hardware upgrading may take some extra money in long run, but newest games are always bit cheaper on PC (usually ~10€, sometimes even cheaper somewhere like GMG), sales are regular and PC also has most exclusives and best backwards compatibility: you can't play 360 game on Xbone, but you can play same games PC version with newer PC - with better graphics and no need to rebuy in HD remake.
And of course if you simply stay on Xbone stage graphical fidelity then you don't have to upgrade your PC for same amount of time! That's what I haven't gotten around why some people think PC should play every game beautifully with higher frame rate, resolution and graphics, even if console versions doesn't.
Actual thing is do you have interest to learn how to build and manage PC or do you simply want to buy games physically, put them in and play. Other thing is that if you are going to buy only few games anyway then it's maybe easier to stick with consoles.
to be frank... this year is not a good year to get new PC or X1 or PS4. because many PS4 and X1 games also coming to PC (AssCreed, Witcher, Ryse, etc) and if your current pc are not strong enough, just play in lower resolution and graphic setting.
To be fair, you could use the argument that "buying a gaming PC" would be a better idea around the end of 2014, when Broadwell hits storeshelves and NVidia releases 800 Series desktop GPU's... because pro's roll on Intel + Nvidia, there's just no question about it....And why is this year not a good year to get a new PC?
Sure, new games on PC usually do cost less. Shame that you have to wait a couple months before they are released on PC if they were console multiplats prior, which was the case with Grand Theft Auto V or Metal Gear Rising, not to look for examples too far. You have the argument of Steam Sales and other such promotions, but Xbox Live and PSN are quickly catching up to the "flash sale craze" and they're organizing their own regularily now. Not only that, but on PC most of your purchases will be digital while on consoles you can always trade one game disc for another at any time in any game store. Both solutions have qualities to them - PC has cheaper games, but consoles have the convenience. Consoles have much cheaper hardware that you don't have to upgrade once throughout the generation, PC's can be freely upgraded, but the upgrades often cost quite a bit, especially during generation shifts when your CPU socket just "doesn't cut it anymore" and your entire setup might as well be trashed because newer, better CPU's or memory just won't work with it. PC offers top quality gaming, but it comes at a price. It's getting more and more convenient and affordable, but it still hasn't reached "console-level" of convenience.