IIRC, the SG13 supports SFX PSUs only with an adapter bracket. I forget if it's included, so check.
I use the C7 in my A4, but in my case, it's right up against the exterior vented panel. For the SG13 or 05, it would be further from fresh air, so I'd probably go with the 120 AIO mounted on the front as an intake and add maybe a thin intake fan to the top panel for ventilation onto the mobo components. Since your thinking a SFX PSU, my recollection is that you might have room for a beefier air cooler than the C7. Take a look at the SG05/13 mods on this site and places like overclock.net to get ideas and ask questions of actual owners.