I just finished building a PC with the Minuet. I like it; it's not a bad case at all.
Anyway, I chose the Gigabyte 9550 that Newegg has listed
here. One thing you have to be wary about when choosing a low profile card is that it includes a low profile bracket. A lot of cards that are advertised as low profile don't include that bracket.
The best performing card I was able to find was a '9600XT' made by Gecube. Although it is indeed clocked at 500/600, it has a 64-bit memory bus - a limitation of the PCB size. It's also very expensive, as only one vendor carries it and they want over $170 for it.
There's also a low profile card based on the 9600 Mobility chipset, but it only has 64mb of RAM and it's very difficult to find. The upside of the card is that it has a 128-bit chipset: a characteristic that is very hard to find in low-pro cards.
Lian-Li made a microATX case a long time ago that was basically a micro tower. It accepted microATX boards, but it had enough room for full size cards. I've been hunting for that case for a long time.