Everything depends,,everythings depends, on what "line" of PC usage you're crossing.
If you cross; like I always have been doing, the 'gamers' line, then a Mid range system can kinda look like this; Intel i7-940, 4 GB Corsair DDR-3 1333 memory, 500Gb HD, Geforce GTX 295. (This is by the way a take out from what PC Gamer thinks is a mid range system, but they are pretty "head-on")
Now this is for the gamer, a mid range in that world might not be mid range in the world of let say a musician or photoshop guy, where huge amount of memory is important and other factors are less important to them compared to a gamer.
My experience with computer/PC gaming since 25 years back is just to balance the system to a stable level and you can run pretty kicked up.
....on the other hand a PC can never be too
big,,,