i'm running bf2 on high res with a 2ghz core duo, 256 x1600 ati gfx, 1gb ram. anything around this spec should be fine. i'm sure there's lots about for about £1k. Toshiba do a decent enough one for less than that if i'm remember correctly. sony are probably overpriced for the benefits they offer. Important thing really is that you don't get on board gfx....need at least 256meg imao

good luck.
fyi i'm using an macbook pro, but that's only worthwhile if you need to run Windows XP and apple OSX on the same machine - which i do.
Nice to be able to dual boot tho, and very easy to set up. the new cheaper mac lappys wont cut it for games - poor gfx.