buying an imac...

Despite the smaller screen, I'd probably still aim for the Intel Mac. You may as well have the latest technology.

Either machine will be a massive leap up from the old PowerBook though.

The 20" screen IS a big deal.
Also, according to MacWorld, your applications like Photoshop will run at 1/2 speed under Rosetta until they are upgraded. Performance of Reason is completely up in the air... Check Propellerheads' websit to see what they say about Rosetta compatibility.

If you need to use the apps NOW, then go for the G5 20"

I'd get the Intel 17". In a few months the Universal Binary versions of most of the major software titles will be flooding the market, making Rosetta more of a perk than a necessity. Plus, down the road you can always toss a 2nd monitor along side the Intel iMac (since it has a mini-DVI plug) if the 17" screen is too cramped.

Either way you're getting more screen/resolution than the TiBook, so don't worry too much about that. If you need FCP/Photoshop NOW, the G5 is the only choice. If you can wait until March for FCP Universal, get the Intel and be happy for the next 2-3 years. My guess is that once Apple gets their Pro apps native on Intel, they'll be significantly faster than their counterparts on the G5.

So I vote for the Intel 17" plus a second monitor a year or so down the line.

Sell that 60 gig iPod in your sig so you can afford the 20" Intel iMac.

Actually, I agree with the poster who said that if you need to run Photoshop/Reason/etc. now, then get the 20" G5 because it's the only option.

If you can wait 3 or 4 months, perhaps the universal binaries for the apps you use will be out - and in that time you could also be saving some money for the 20" Intel iMac.