Which iMac for 'light' video work?

Hi,

I'm about to buy a Mac. Not that I'm uhnapphy with Windows platform at all (I'll be still using it). Just wanted to test something new (especially Final Cut Studio opposed to Adobe products I'm familiar with).

Let's say I need it for 'creative' stuff. Not iMovie/home movies work. Not heavyweight video editing either. I don't consider myself a 'pro' as far as editing and compositing are concerned, I rather do creative side of TV and video projects (edited on Avid or Premiere/After Effects) than edit them myself.

I need something for home (let's say... a 'scratchpad') and I thought iMac would be a good choice.

The background... I've done a lot of research about technical differences, benchmarks, video cards comparisons etc. regarding the new 20 inch iMacs.
I also asked a few people working on Macs but most of them were using Mac Pros, so not much help there.

I'm aware that the processor speed is not crucial, I'll be using external hdd so original disk space is not a problem, I'll be adding extra RAM anyway. So if it was just these features I would go for the lower model.

But the question is the video adapter in both iMacs. So my questions to 'more experienced users'...

1. Do you think there would be there a noticable difference in typical editing work in Final Cut or Premiere (previewing clips and basic transitions and effects, scrubbing, layering) when using lower and higher models?

2. I understand that the extra video RAM in the higher model may give some boost in the Motion application. Is it correct? BTW, on this page http://www.apple.com/finalcutstudio/specs.html these ATI 2400/2600 cards are not mentioned for Motion

3. Will it make any difference if I decide to use second monitor connected to my iMac one day?

The answer I found on forums is 'if you can afford it get the highest specs available' but... well, I don't like spending money on something I don't really need

thanks in advance

Pete

The extra 128megs on the HD2600 would come in handy in Final Cut.

The Radeon HD2600 works fine in Motion I understand, so I'm puzzled why it's not listed.

But when buying an imac the question is not will you need now. But in a few years time will you need a certain feature of it. Sure you don't need the 24 inch model now but I think in a year or so you might be wanting it's graphics or screen real estate. This is cause macs tend to last for a long time before they die or are truly outdated.