Without knowing the specific motherboard of that prebuilt, I can't tell you if it's gonna be compatible with an m.2 ssd, so I'd go for a sata 3 one just to be sure, like the 250gb 850 evo for $99, there's a deal on a $62 ssd right now as well as many around $70 for 250gb, but honestly I'd rather not cheap out, if you're going to buy a build that expensive you might as well pay the extra for an 850 evo, you can see the prices here, it's a rough list since pcpartpicker misses on many deals and sites, but should get you a good idea