I disagree. It's all about balance. If you were building a new computer, would you pair a single 1680x1050 monitor with a pair of 6970s? No, you would be defeating the purpose of spending $700 on a GPU setup by only spending $130 on a monitor. Yes, you could play Crysis with all the texture packs you dreamed of, but it would still not look as impressive as a monitor with a higher resolution and better pixel aspect ratio.
What I've notice is that generally you will be able to max out (8x AA, 16x AF) and still be able to play almost all current games by spending twice as much on your GPU as your monitor setup. For example, a good 1080p monitor is around 150-200 (ignoring sale prices, we're just considering the actual value of the monitor), so if you spend 300-400 you'll not be lacking for GPU power. At the high end, a tri-1080p monitor setup costs around 400-600, so spending $1000 on a GPU setup is perfectly justified, and will definitely run all games at high settings. It doesn't apply to all games and all monitor setups, but when trying to determine a budget for a GPU given a certain resolution, it works quite well.
In the OP's situation, a good 1440x900 is around $100, so any GPU at around $200 is going to work and get the job done. 2 years ago I bought my friend a GTS 250 for that resolution, it cost $150. He could play Crysis at medium- had we spent another $50 and gone for a GTX 260 he could have played at high.
BUT for some people its not enough; like i say, there its nothing like crank every single option to the max and enjoy a superb gfx experience without any kind of slowdown; and thats why some guys go crossfire/sli with monster cards at 1080p only
And like i say: in some games (depends on the engine ofc) you can see a difference between 30-40 FPS and 60 FPS, and even more with details maxed
I realized you speak about balance money related, but sometimes the results its not the best you can get