Upgrading My PC* | EDIT: Building PC - Help with parts.

[Strika]

Yes the combos are compatible. You are getting it now, AMD CPU runs with AMD mobo, and Intel runs with intel. You forgot power supply there. It doesnt really matter about your case, they all are pretty much the same inside, bigger or smaller it should fit as long as it is mid tower ATX case.
And you cant use external drive without the hard drive in your computer.

Setup 1: Good Gaming rig, that would run games like crysis and gta 4 without lag, also any game basically.

Total price: $1095.50

Case: http://www.centrecom.com.au/catalog/prod...s_id=29005
Processor: http://www.centrecom.com.au/catalog/prod...s_id=29360
GPU: http://www.centrecom.com.au/catalog/prod...s_id=33046
RAM: http://www.centrecom.com.au/catalog/prod...s_id=30039
Motherboard: http://www.centrecom.com.au/catalog/prod...s_id=37779
PSU: http://www.centrecom.com.au/catalog/prod...s_id=30765
DVD-ROM: http://www.centrecom.com.au/catalog/prod...s_id=38162
HD: http://www.centrecom.com.au/catalog/prod...s_id=37086

Setup 2: Can run GTA IV but is less more advanced gaming rig, graphic card and power supply changed.

Total price: $810.60

Case: http://www.centrecom.com.au/catalog/prod...s_id=29005
Processor: http://www.centrecom.com.au/catalog/prod...s_id=29360
GPU: http://www.centrecom.com.au/catalog/prod...s_id=33870
RAM: http://www.centrecom.com.au/catalog/prod...s_id=30039
Motherboard: http://www.centrecom.com.au/catalog/prod...s_id=37779
PSU: http://www.centrecom.com.au/catalog/prod...s_id=30877
DVD-ROM: http://www.centrecom.com.au/catalog/prod...s_id=38162
HD: http://www.centrecom.com.au/catalog/prod...s_id=37713

Both rigs are really good for gaming.