Overall, I was happy with my experience with the Antec Sonata Plus case. Build quality is solid, and installing the test system was easy as far as cases come, even when using a relatively large heatsink like Thermalright's Ultra 120.
With the test platform's video card, a reference 8800GT, there was ample room for installation. It should be noted that with this video card, the hard drive tray parallel to the video card would be blocked from use. So if running an 8800GT in SLI, two hard drive trays would be blocked from usage.
Measuring the room available, the maximum length for a video card is 10". This means the Sonata Plus can accommodate ATI's X2900 and HD3800 series video cards, and most of nVidia's 8800 series video cards except for the GTX and Ultra (which are both 10.5" long).
Antec did a good job with the Sonata Plus 550. Out of the box, they provide a good matched up case and power supply. I found the case to be well constructed, with all parts fitting solidly, and no visible defects. Performance wise, the case handled the test platform with good temperatures and quiet operating noise. The only qualm with the case is that we wish that Antec would extend the case by an extra 1-2", so that higher end video cards can be accommodated. The 8800 GTX and Ultra will not fit in the Sonata Plus, and if reports are correct, next generation 2-GPU video cards won't fit either. This isn't a big issue however, since for the main target market for high end video cards usually opts for higher end cases as well, of which there are other cases in Antec's lineup which would be better suited. As a full package, circuitREMIX is proud to present Antec's Sonata Plus 550 case and power supply combination a 9/10, and an award!