http://www.flatpanels.dk/panels.php
Type the model number of the screen you want into this.
It will tell you the TFT panel used to make it.
Copy paste this back into the search.
It will tell you all the manufacturers and the models on the market that use the SAME panel. Believe it or not but many Apples, LGs, dells, samsungs, Phillips, Acers etc etc use each others technology and stick their branding on the front.
e.g. was just about to buy a Dell 2007WFP 20" TFT with 25% off ...... to find out that phillips are selling the same thing with a different model number and brand name on the front for £50 less (from ebuyer or Amazon). You can confirm this yourself using the above link. [edit - the Dell has had another price drop and now is similarly priced with quidco discount].
However in some cases, cheaper is not always better. If you know a particular brand does shocking customer support, perhaps the extra few quid is worth it. Howrver in my case .... i aint spending another £50 for the same thing. (well .... phillips have decided to spray theirs silver not black In addition the support differences, some may come with a USB hub or speakers integrated - this is down to each manufacturer.
To find the best price is it worth copy pasting in each model number into a price comparison site like froogle and kelkoo and seeing what comes up.
Hope this helps.
