I would recommend not getting an LCD TV, they aren't nearly as accurate as a nice LCD monitor. Plus, the resolution is terrible. You would have to get a 1080P and then if you go too big your pixel pitch will be super high (big pixels).
You need a crisp display with high resolution that produces colors accurately. PVA/MVA panels are nice, Eizo uses though actually for the the high contrast ratio. S-IPS/H-IPS etc are the highly regarded for their color reproduction and viewing angles.
The Dell 24" is a PVA panel and has a myriad of issues. One could be fooled since Eizo uses PVA, but the difference is in the processing and electronics which are much higher quality in the Eizo. The Dell is ok though, it can be had for under $550 if you wait for coupons and what not. The current 2407 is ok, you will have deal with a terrible backlight and the other inputs are mostly garbage.
20" panels are mostly nice. Dell 2007WFP is good, I had one, just sold it to go larger. The NEC 20" ones are good as well, more expensive as well. 24" seems to be the sweet spot for price right now though. Also check out the LG 245 and 246 as well as the Samsung or NEC (NEC is pricey). 23" panels are dying, but I believe they were all S-IPS. The ACD 23" is S-IPS.
22" displays are all TN panels. They are quick but do not have color accuracy or good viewing angles. I would stay away, but they are cheap.
It really depends on if you make money. If you make money on this stuff, go all out. It will pay off. However, color is really only key when you are printing or in a color controlled environment. You can calibrate a Dell to be fantastic, it will print pretty accurately, it won't have a high color gamut as it is only 72% of the NTSC color gamut (The new 2407WFP-HC has 92% and better backlighting, unavailable right now in the US). But it will be decent. If you are printing for profit or for clients... I would go a little higher end.
I hope that helps a bit. I am currently looking into displays and I always try to keep up with what is going on, so if you have specific questions I am more than happy to help.
Also, as far as the ACD goes, if you would like more inputs the Apple is not for you. They are lovely, I owned the 23", but then I got a 360 and it was a no go without some expensive equipment.
