IPS, MVA and TN refer to the type of panel used in the display.
The cheapest (and generally worst) displays use TN screens. The best (and usually most expensive) use some form of IPS.
I'm using an HP L2335 23" widescreen dislpay, which uses the same IPS panel as the Apple Cinema Displays (or at least it did at time of manufacture. I haven't checked if Apple still uses these panels).
Ironically, the new 24" version of my display uses an MVA panel, which is MUCH brighter, but not as colour accurate.
You might find it interesting to note that I picked an L2335 up off ebay for a friend last year for £320 - new with full 3 year on site warranty.
For reference, you can usually spot a non-IPS panel by its contrast ratio. IPS panels tend to have contrast ratios in the 400-800:1 region. Non-IPS panels always boast of much higher ratios.
The HP LP2065 looks like it might sit well in your budget, and would be a good choice for you as long as you didn't mind working on a non widescreen format.