Ivy Bridge Core i3 CPUs are not out yet so if you install a Sandy Bridge i3 CPU in a Z77 motherboard, then just aware that the PCI-e 3.0 slot will operate in PCI-e 2.0 mode. Not a big deal yet since so single video card currently out can max out a PCI-e 2.0 slot's bandwidth.
If the choice is between #1 - Core i3 + Radeon HD 7750 and #2 - Core i5-3570k using only the integrated Intel HD 4000, then #1 will provide you with better performance in games.
The Intel HD 4000 is about as powerful as a Radeon HD 5550 or HD 6450... so it is slightly slower than a Radeon HD 7750.
Hey, Thanks! That answers my rather rather vague question. Appreciate it!