my budget is 700 I might even got 800
custom build one, with highlight on those parts:
- at least 4 gigabyte of RAM (prefferably more)
- a mid to high range GPU, really make sure you buy a good one cause they are not cheap and make the most impact.
- a modern CPU as high as you can afford, this has less impact then the GPU but is still importent. you don't need an Intel ICore 7 really, an ICore 3 or ICore 5 will do the job just fine (espacilly the latest Haswell ones). performance is on clock rate rather then number of cores (3.5GHZ dual core is better then 3.0GHZ quad core).
- the rest goes to peripherals and other stuff like casing and screen. those don't matter a whole lot and are relativilty cheap.