i think some people are too power hungry these days stating a 4870x2 is the min for smooth games
i have 2 30" hazros and my spec is a old 939 4800+ o/c with a sli setup of 2 evga 8800gt ko (faster than a ati 3870x2) and i dont have any problems in running native with min 2x aa (cant tell the difference any higher than 4) and min 8x af tho i prefer 16x.
tho if by chance i had any problems id just go down to 1920x.
games played recently are:
HL2 2 episode everything on full 4x aa 16x af
call of duty 4 4xaa 16xaf
call of duty 5 2xaa 8xaf
assassin's creed
dead space everything on full
by and large yes my fps were not in the hundreds but games were all smooth, above the 50fps mark and by and large i couldnt really tell you the difference in playing at res 1920x and 2560x as games iv noticed dont tend to blur anything like text does (text has a slight haze when not at default res but its really not that bad) when not at native.
later towards the end of the year im upgrading anyway as this system was built and added to over the last 3 years and when it comes to that day the cards will be cheaper.
me id always go for the 30" although it depends on your budget (i got mine at special offer price at christmas
2 for the price of 1 dell
) as once you got it its a keeper compared to computer gear which is upgraded frequently and if a game does slightly struggle some where down the line you have the option to knock it down to 1920x and below whilst if you went and got a 26" or 28" your max is 1920x and below also you lose the extra 2"screen space and have to put up with a lot higher dpi making everything fonts and imagewise looking slightly blocky.
anyway the choice is yours at the end of the day as might find you like the larger font on the 28".
just my 2 cents
HRhino