You won't afford the M10 for under $2k, and there's no reason to get it, as he stated he was a casual gamer. Go for the M9 if it's available in a system under $2k, the 32MB version should be fine. (otherwise the G4G is your only option, and is both slower and less advanced than the M9.) The M9 supports pixel and vertex shaders, important features of newer graphics cards, however they are not the latest version 2.0 (and i'm not quite sure of the implications of that.) I do think an M9 is more than enough, however, for your price range.
Ways to save money:
Get a smaller screen (14")
Get a regular XGA+ screen, (not SXGA or UXGA) which supports a max resolution of 1024x768, which should be fine unless you feel you need to go higher (there are other reasons for a UXGA screen, scaling for one, but you are trying to save moeny.)
Get a P4 2.4 GHZ at most. That's more than enough. The processor will be the last thing to be outdated on the machine.
Get the cheapest thing they offer for memory and then buy your own from crucial, as they are overpricing it outrageously.
Don't get the Inspiron I8xxx line, get the "value performance" model, which alludes me at the moment. If you don't get a Dell, the same thing applies for nearly all manufacturers.
Get a 32MB graphics card, perferably an M9
Get a 30GB hard drive.
Don't get a CD-RW. This I don't recommend, however.
Not getting a floppy drive will save you about 30 bucks.
Get a 2 year warranty.
Whatever you do, DON'T get onboard/shared video.
