I disagree about the Corsair RAM. corsair is not as fast as it's made to be.
and yeah, by far go for the 4400+ over the monitor and 7800 GTX. you already have a 7800 GT, which you can softmod for the extra 4 pipes. (you don't even need to flash the BIOS, you can do it in Rivatuner) and an extra 2" of monitor won't really do all that much. and it doesn't increase performance.