Can't comment on all ( actually not on most ) but I do have a few comments / thoughts since I've just been GPU shopping and use "big" screens.
Depending on what type of games you play and the monitor you buy ( does it support 2560x1600 - the one u posted doesn't ) i.e u'd run 1920x1200 then ya GPU might be overkill for current scenarios.
http://www.anandtech.com/show/6159/the-geforce-gtx-660-ti-review/10
If you look at that one u'd see what the 9790 pulls in framerates at max settings and 16 AA - if you look at the other games u'd see u in most if not all cases can go w something cheaper/smaller.
Personally I ended up w a Gigabyte Nvidia 660 OC because the OC ed has 2 fans and very good noise vs temp and pretty good performance - Gigabyte also has ATI ed's w that look for Windforce mark on their website ( the ti ed is there in the link but there's also a regular 660 reviewed somewhere on Anandtech ).
ATI or Nvidia? depends on prices in your country and what u feel fits your needs the best --- I go back and forth between them. ( and you can always SLI later on if performance becomes an issue...the GPU will be rather cheap then to pick up a 2nd ed of if the mobo can handle it...did not check! )
Personally I'd also go for a bigger monitor - I have a 27inch HP 2710 - 3 years old and out of stock...but personally I'd rather spend 100 euro less on a GPU ( than overkilling it ) and get more screenspace
Especially if you also need to do autocad, if you program or other cases where screen space is nice. ( unless you go dual monitor ).