Remember that the VGA Booster is also dual +12v with an 18A rating on each rail. The system I'm using to test with is an overclocked AMD setup with a single graphics card.
6400+ A64 X2 @ 3.4Ghz / 1.5v
Biostar TForce 570 SLI @ 283x12
2x1Gb OCZ Titanium PC2-6400 @ 566Mhz / 2.4v
XFX 8800GT @ 792/1080
First up I put in the 450w power supply by itself to see if it can even run the system, especially with a load.
I was really surprised that the 450w power supply handled the demands of this system, and actually performed pretty decently. There was almost two tenths of a volt drop on both +12v rails and the +5v did go up slightly, but overall it did better than expected. I did notice that under load testing the fan in the power supply was very noisy, it must have been running at full tilt. Now let's see what effect adding the VGA Booster has.
With the video card plugged into the PCIe1 the result is a very slight reduction in output compared to the unloaded PCIe2. But this is only a hundredth of a volt, certainly some small difference is to be expected. Of more important note is the effect on the 450w power supply. Notice that the range of fluctuation between idle and load outputs is now much more closely controlled without the extra draw from the graphics card. The system power supply also quieted down considerably; it was definitely less stressed.
The Sirtec VGA Booster certainly does what it is designed to do. It allows you to run your video card(s) from an independent power source, which frees up your system power supply to handle everything else. Even though in this test the system power supply was able to handle the load for several minutes (long enough to log voltages), it was obvious that transferring the load of the video card over to the VGA Booster helped relieve stress put on the system. I would not want to attempt to run this system solely on the 450w power supply long-term. Considering the draw of the CPU and GPU alone, the 450w power supply was likely near maximum capacity. Although their rated TDP is only 125w and 105w respectively, remember that this is the Thermal Design Power rating, which is an estimate set by the manufacturer in order to size a cooler appropriately that will handle the average heat generated by the chip. The actual wattage drawn by the overclocked processor and video card at full load are likely much higher.
The quality of the Sirtec VGA Booster and its accessories is very good. The power supply itself feels very solid and has a rough, durable finish. During testing I did not see the fans come on at any time and the unit did not even get warm to the touch. The power cables are all sleeved and have color-coded ends. Of course I did have a problem with the power cord being the wrong type, but this is likely due to the review unit coming directly from Taiwan, rather than through regular retail channels. I also did not care for the main ATX adapter cable; the separate 4-pin plug does not attach to the main in any way and the connector is very difficult to get seated on the motherboard due to how tight it fits in the socket.
I was only able to find the Sirtec VGA Booster for sale online at a handful of foreign websites. At one it was selling for 59 Euros, which translates to roughly $86. Another site had it listed for 256 Ron, which equates to $105. And a Canadian site was selling it for $99.99. So depending if you can find this unit for sale in the States, it will probably cost somewhere around $100. When you consider how much a quality 800w+ power supply normally goes for, adding the High Power VGA Booster to supplement your existing power supply seems like a deal. For those looking to upgrade to a single high-end or multi-GPU based system, and currently have a power supply rated in the 400-600 watt range, the VGA Booster may be just what you need.