For multimedia/browsing/gaming, go with the 24" screen, especially since the decision is between 2-19" vs. 1-24"; if you were trying to decide between 2-20" vs. 1-24", I would still go with the larger panel, but would not mind the two 20" monitors either. 12x10 is just not enough desktop space for me, even in dual config- I would rather buy a single 20" and add another 20" when funds allowed.
If you did a lot of work where it would be advantageous to separate things (i.e. spreadsheets) and planned to use the monitors primarily for work, dual 19" would be OK. In your case though, I would definitely go with a 24" panel. I have used 17", 19", and 20" LCDs, and now run a 2405 with a 2001FP. The 2001FP is turned on only when I have work to do- for everyday browsing or gaming, the 2405 is the choice, hands-down.
Going from a 19" (12x10) to a 20" (16x12) was a HUGE difference- going from 20" to 24" (19x12) was equally as impressive. There is no way I would ever go back to anything less than 16x12 (or 16x10 WS).