Generally there's not a big difference between an i5 and i7 for gaming. An i7 is quite similar, but has hyperthreading (which doesnt often help and sometimes hinders gaming performance). Additionally intel cpus, minus the k series are pretty much clock locked these days.
As for i3, its far from crappy. A modern i3 will outperform older i5 and i7's in lighter threaded software on occassions, and is very power economical. And lastly, as of hd4000, intel gpus are no longer terrible (they'll beat earlier apus from amd.
Lots of uninformed, innacurate "information" being spewed here, but I guess truth and accuracy arent really the point of the thread.