Well I had my heart set an an Antec Sonata Plus 550 because I loved my old Sonata case and have it out for as quiet a computing experience as possible while still having to push the performance envelope.

After searching the ol' Internet, it seems that the GTX 260 won't in fact fit into said case without a fight. As such I am looking at a few options:

1) Find a supremely quiet case that also has the clean, understated looks of the Sonata case. No clear windows or LEDs! Ideally it would remain as small as possible.

2) Figure out what the best NVIDIA GPU is that fits inside of an Antec Sonata Plus 550 and go with that...

If you have an answer or suggestion for either of these two questions, I'd love to hear it!

The 8800GT is no bigger than the width of a standard ATX motherboard.
I have one each in an Antec 900 and 300 with out any troubles.
Sometimes on Amazon you can find the 300 for $50 shipped at that price it's a great case.

Thanks, maybe I'll just look into the 8800Gt.

Does anyone know if the new ATI cards fit into this case? Looking at the specs it looks like one of those 'tight but possible' situations.

Still browsing around for similar cases that are slightly larger as well, but we'll see.