I searched around a bit but I couldn't find exactly what I was looking for.
For gaming does the difference between a TN panel and a non TN panel make a big difference in the quality of graphics? I plan on building a high end gaming computer and I don't want to get a TN panel if it is going to be noticably worse.(although money is a concern)
TN panels tend to have more color shifting than any other panel due to the limitation of the technology itself. Color shifting basically means that the color can look washed out or in the case of some TN LCD monitors the colors will look reversed (red looks blue, black looks white, etc.). The reversed colors would only appear at more extreme angles, but as for color shifting, that can occur by simply moving your head.
One good thing about TN panels is that they are "rated" as fast as 2ms response time. However, under typical conditions these "fast" panels can be as slow as 30ms or more. However, all LCD monitors is exhibit some level of ghosting regardless of the response time. It depends on how well (or poorly) your brain processes the info your eyes transmits to it.
I've seen ghosting on some 2ms LCD monitors whereas others could not percieve any ghosting on those same monitors. If your brain/eyes can pick up these minor variations then it sucks to be you (and me too).
Would I ever buy a TN monitor? No, not for my primary monitor. However, if the S-PVA panel LCD monitor connected to my secondary PC (which I don't use much), then I might just spend the $200 - $300 on a monitor that I won't be using much.
178/178 = Non TN Panel. Anything less like 176/176, 170/160, 160/130 is TN.
Price is also a factor. Just about all 22" LCD monitors are TN. The exceptions are Lenovo Thinkvision L220x (1920 x 1200 resolution) selling for $450 - $500, and "consumer" level 22" monitors made by Eizo; starting price ~$650.
24" LCD monitors not using a TN panel generally start at about $600.