IMac G5 Graphical concern

I'm currently looking at two system to replace my old G3 Beige 300 mhz (over-clocked mind you) mac tower, also have a G4 laptop.

What I'm having a problem is deciding over is either getting the the 20" 1.8ghz Imac G5, or Single 1.8 GHZ G5 tower. The main conern is that I like to pick up games time to time and play them, so I'm just curious if anyone has used the Imac G5 to play any new games, namely Halo, Tron 2.0, and unreal tournament 04' etc... and if the Geforce 5600 fx 64 mb can handle them at decent rates (Seriously Apple turned off the gaming community off by this, but then again heat issues and price could have been the deciding factor) I've tried playing Unreal tournament 2004 on the 1 ghz 12" powerbook with the 32 mb geforce and it was just... well a complete joke. I just don't want to buy a new computer that can't handle modern games, cause honestly it's just a laptop then and a reason why I want a bigger system.

If anyone has benchmarks for these games etc... or have played them on the New Imac g5, I would appreciate any response

I know it's not the precise answer you wanted but I don't think it will have too much trouble playing current videogames. PCs are still really the best bet for gaming.

I have halo for my 1.8 imac and works fine and i can turn the settings right up but on some levels i have to turn em right down for some reason? i have em full on in multiplayer though and works like a dream but dont consider getting it to play
Doom 3, half like 2(which has no mac release... yet) with settings turned up full but i bet ya it will be able ta run it but i'd go for g5 tower with upgraded graphics card(but then you have to buy a moniter)