I'm looking at replacing my samsung 19inc monitor for a 24inch (maybe 22inch) widescreen for gaming. the only real reason behind it is i want a bigger picture when i play.
 
my question is will my machine benifit from a 24inch monitor being used mainly for games like company of hero's COD4 and crysis. or will i notice a serious FPS drop.
 
Q6600 oc 3ghz  
EVGA 750i ftw
4 x 1gb corsair xms2 ddr2 pc6400
2 x 8800gt inno3d factory OC
650w silverstone zeus
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currently i get around 90FPS on COD4 everything maxed out AA 4, COH 60FPS everything maxed out no AA
crysis medium around 30-40fps.

A 24" lcd monitor wants to play at 1920x1200, it's native resolution.   If you currently are at the same resolution with a crt, there should be no difference.   If you are playing at a lesser resolution, there will be some impact.   The question is, will it be a serious drop that will affect your gameplay.  I suspect not.  http://www.guru3d.com/category/vga_2/  
Also, most LCD's refresh the screen at 60hz.  A system that can deliver more than that constantly is overkill.

A 24" LCD monitor doesn't "want to play at 1920x1200". That would be yourself the player. A monitor can be set to play at native resolution or lower resolution depending on what resolution the GPU supports.
 
Playing at less than native resolution will impact image quality because there is a fixed number of pixels and there for a process of interpolation must be used to estimate where pixels should be placed on the screen.
 
Some LCD monitors can have better image quality at lower resolutions better than other LCD monitors, but image quality will never be as good as native resolution.
 
A few 24" LCD monitors offers 1:1 pixel mapping which is the ability to use the specific number of pixels on the screen based on what you set the game resolution to. The playable viewing area is centered and the pixels that are not used will generally be black or off and creates a "border" around the playing area. This will maintain image quality because the monitor itself goes into an "emulation mode" where it acts like a monitor with lower resolution.
 
Check out the Dell 2408WFP which has this feature.
 

So if your native resolution is at 60 and you up it to 75 what's the drawback...if any...and do you get any benefit or is it not going to get recognized anyway...

A native res isn't 60 or 75, thats the refresh rate.  Back in the days when people used CRTs, refresh rates mattered.  Remember that with CRTs, the gun starts at the top, and starts drawing the image as it moves down.  The faster this happens, the better the image looks.  The down side is that you need hardware powerful enough to deliver that many images.  If you have a higher refresh rate then you can draw images, some with get drawn twice.  This has a negative impact on how fluid the game looks.  If you deliver more frames then your monitor can draw, some of them get skipped, again effecting how fluid the game looks.  Read up on refresh rates and Vsync for more info.  None of this is a problem with LCDs as they have no refresh rate.  They turn the pixels individually on and off.
 
If your native res is 1280x1024, and you up it to 1900x1200 (or 1680x1050 if he gets the 22" screen) then your hardware needs to be able to push that many pixels.  If your hardware is lacking, then your FSP will drop.  The advantage is that you can see more of the game at one time.  This is very valuable for RTS or RPG games.
 
For the OP, seeing as you have 2x8800GT, you'll probably alright.  This setup should be a bit slower then the 9800GX2.  There might be a game here or there that doesn't work well with SLI, but you should be good for the most part.

My point was, that image quality is best at native resolution, so there is where you would like to play if you can.   You can play at lower resolution than native, but never at higher.   With CRT's, a high refresh rate was necessary.   Without refreshing, the pixel on the crt "died" or dimmed out.  It needed to be repainted, just to have a picture.   At 60,hz, you got a "shimmering" effect, which was tiring on the eyes.  A good CRT at 75hz, or 85hz gave you a steady picture.   With a LCD, the pixel just stays where it is set, and the only need for a decent refresh rate is to change the picture.   If it can do this at 60hz, as most do, that is all you need to see a clear  picture when there is motion.
24" is 1920x1200.   Some monitors can be 26" or 27" and still be 1920x1200.  The pixel size is just a bit larger.   TV monitors that are called 1080P are also 1920x1200, and can come in any size.   I don't know what their refresh rate is.
 
I would love to find a 40" monitor at 2540x1600.  30" seems to be the largest size for that.

24" is good if you ever get a blu player , 1080 can be done then.  My single EN7800GTX can run a Samsung T240 at native 1920x1200 with no problems.  Halo 2 and sins of solar empire run smooth.  I havent tried more taxing games yet but I could imagine a problem with allot of fast moving stuff all at once.  You definitly have enought power for a 24" screen.   Once you get a 24" you can't go back.

+1 for the Dell 2408
 
Yes, you will notice a drop in your FPS but your games will still be more than playable with SLIed 8800GT's.
Assuming that you are gaming on a LCD at 1280x1024, you are probably CPU bound as it is.
Raising your resolution will let your GPU's use more of their potential power.

The Dell 2408 is a great choice.
 
Oh, and 1080P is actually 1920x1080, not 1920x1200.

+1 for the dell 2408 , if you want 22" then as everyone will agree it has to be the samsung 226bw

Its not allway overkill. If your average fps is around 60  lovest can be often under 20 and its also lowest fps in intense scenes thats matter.
Now if you have 100 average, display cant show it all, but when occasionaly fps drop it usualy dont go under 60 at least not often.
there are diferent type of games and i personaly want to have 30+ fps in strategies and 60+ in shooters and MMO's.

ofcourse LCDs have refresh rates, its little diferent from CRTs, but basic principe is same, how many time per second you can redraw screen.  

Yes, but it's less relevant.

 
The 226BW has been discontinued long ago.