Some monitor questions

I'm going to be purchasing a new monitor tonight--One of mine was damaged moving. I currently use two identical 24" widescreen LCD's that have 6ms refresh and a native resolution of 1920x1200. Now, my questions are:

Since I'll still be using one of them, should I get another monitor that has the same native resolution? If I don't, will it affect PiP swapping with ISBoxer? Should I get one that has the same refresh rate, or will it not affect anything vis a vis performance working with another monitor with a different refresh rate? Is 6-8ms decent nowadays (these are 3 years old) or should I be looking at 2-4ms?

Thanks in advance! :)

I'm using a 22" 1680x1050 (master) and a 24" 1920x1200 (slaves) screen for my boxing. I think the important thing is same aspect ratio (for fiveboxing at least) so you don't get stretched or compressed views when switching.

alas i read somewhere that it is better performancewise to have the same resolution on both screens. i won't put my hand into fire for this, though.
6ms is not refresh but switching from gray to gray (presumably) of the pixels (in german it is "Reaktionszeit" which translates word by word to reaction time.
refreseh rates of LCD's should always be either 60 or 75 Hz. (or 120 or 200 for extreme fast 3d displays or something, but mostly 60 or 75). but even if you get a faster one it should be able to display at 60 Hz so they both can use the same vertical sync which is again important for performance i think. don't quote me on that one either ^^
imo buy a decent brand and go for what you can afford without hurting yourself instead of looking for a 2-4ms one. those extreme stuff really seems to matter only in shooters. if you play shooters, too and do so on a very high level you might want one of those fast displays, for wow i don't think it matters that much...

I love Dell. I really like them. I only use the Ultrasharp models, due to color, timing and resolution (16x10). U2408 was my last (have 3 of them). Bought a U2711 (on sale for $899, 250 off) and love it. Longing for a U3011 (just released like a month ago, think about $1200-1300). Sure they are expensive, but I like the theory that is the thing you look at most and get the best you can afford, since you can't upgrade it.

Two was to think about it. Either buy the same as you have now, or just run the new monitor as the older resolution. SC2 is jacked up that 16:9 show more space than a 16:10 so I just run my monitor (16:10) at 16:9 for SC2 only.

I started playing on 2 24" 1920-1200 monitors. When one died 3 weeks ago I replaced it with a 23". The other 24 died 2 days ago (both seems to suffer from the bad capacitor syndrome). So they are getting repaired now as they are still in warranty. I still had 2x 17" (1440x800) laying around and a normal 17". So figured for time being that I'd use one of them. Tried out a couple of combinations and currently is use 23 for main and 17" wide for slaves.

I must say that i really like a small screen for my slaves, not even sure if I'll go back to the 24"s once they are repaired. I seem to have a better overview of what's going on.

overview is a very important point here. that's why i use my smaller 22" display for the master and a quarter of my 24" for each slave instead of the other way around.
more than two widescreens are to much to view at once. i use the bigger screen for the slaves so the individual portion of the screen is bigger for each slave (so I can make out details better - or simply so i am able to read the text). i really like the 24" for being able to watch full hd videos but for gaming only i think i would use two 22" screens @1680x1050 so i don't have to move my head as much to see what's going on.

but I think the thread gets a little derailed.
point is: reaction time does only matter for watching fast paced movies/sports or extremely fast games to which i do not count wow. perhaps an avid arena player would differ in his opinion.
refresh rate of any new lcd should be no problem. resolution shouldn't be the biggest point either - except for aspect ratio if you want to use the widely used one screen @fullscreen / one screen @quartered screen layout.

I use a

28"(27.5 viewable) Hanns-G HG281D monitor with a resolution of 1920x1200

and

22" HP w2207 monitor with a resolution of 1680x1050

I had no trouble with isboxer switching, not sure what the PIP feature of isboxer is, I just had master on main monitor and slaves on other monitor. Just have to set it up in isboxer monitor manger.

However, I believe the fast switching of isboxer is more dependent on how "good" your system is in terms of speed and stability rather then what monitor(s) you use. Keep in mind that the more monitors and the size of the viewing area and higher resolution will put a strain on your computer. So a "good" computer will have no trouble with the fast switching of isboxer.