Open her up, captain
The SG05 can accommodate discrete graphics cards that are up to nine inches in length. The GeForce GTS 250 512MB fits the bill, as would a Radeon HD 4850, and we'd probably take the latter if given a direct choice.
The ASUS card's 'Glaciator' fan connects to the PCB via two wires and spins up at a fixed, irritating level at all times, enough for it to be distracting from 10 feet away when housed in the small chassis. There's a method of quietening it down by reducing the fan speed via RivaTuner software, to the extent where it's around half as loud (at the expense of higher temperatures), but Novatech should have done this at the factory; many novice users may not know how. ASUS' own SmartDoctor software doesn't work, we noted.
The card doesn't block an expansion port from being used; there's literally no more space on the motherboard as the PCIe x16 connector is on the very edge.
Wiring is a little unruly inside, bunched together between the CPU and hard drive. Again, we don't understand the rationale for a 320GB drive on a high-end system; the price premium for a 500GB drive is just £5.
The intake 120mm fan is one of four in the system, with others on the graphics card, CPU, and PSU. Add them all in together and the system's not the quietest when idling in Windows; each fan produces a different pitch. Place the Allspark under prolonged load and it becomes noisy - the sound seemingly amplified inside the small chassis.
One of the reasons is down to the half-height PIB cooler on the Intel Q9550S chip. There's ample room for a full-height cooler to be installed, and we'd recommend that Novatech does so, reducing the combined noise.