19" or 20" for gaming?

hi, im thinking about getting a HD3850 256mb and i was wondering whether it will be ok to use with a 20" monitor (1680x1050), or should i stick whith 19" because of the memory? the monitors im looking at are a Dell 19" SE198WFP widescreen and this AOC 20" which is only NZ$24 extra:

http://www.aocmonitor-anz.com/lcd_monitor/203vw.php

is it worth losing performance for a slightly larger screen? i would go with the 512mb card but its not much cheaper than the 3870 here and im trying to keep costs low. thanks.

I expect older games will be fine with 256mb, but I think newer games will start to uncover the memory's limits, and reduce the perfromance alot. Its probably best to go with a 19", which is perfect for the 3850.