This is a tall order but can be filled if you are willing to make some compromises. Most SFF lowrise cards either use only one output or use a ribon cable connected to a full size bracket for one of the dvi or vga connectors. If you want dual monitors your best bet would be to get a card that uses the ribon cable style and make your own brackets or use some that you already have. This would take up two slots but its about all that you could do to get two good connections for monitors, aka not using svideo for a monitor connection.
Also most SFF lowrise cards are the bottom of the line gpu's that use turbo cache or similar system memory useage tech, so you could get 256mb easy but getting dedicated 256mb may be hard to find while keeping in line with all of your other demands.