I missed the G5 thing (could not buy a new computer for 3 years now with 2 little kids) and left off with a titanium 800/ 3/4 gigs of ram.......Finnaly I can buy a new mac

My collaborator has an imac g5 ppc 3/4 gigs of ram. He uses logic, I don't go there.....So I installed my dp on this machine to enable artistic flow.....
We are guitar/bass/reason (with a decent amount of devices....) and synths.
Frankly the performance is no better than my washed up 4 year old powerbook (with the internal drive). Constant buffer/playback/latency issues..... (my buddy says logic runs smoother)
our whole creative vibe depends on on the fly/improv, so I need to be able to keep the buffer settings low while I jump in and out of being a guitar player and programming in reason.
I'm not "your company's computer guy", but I know how to set up a decent DAW/opperating system all the do's and no/no's.....
Am I "way out in left field" to say that between mac os updates/dp updates/ reason updates, etc..... machines are not that much faster than the dreaded os 9 days?
Maybe it is a blessing in disguise that I could not affor a new computer until now.
I'd love to hear feedback from those who upgrade macs every 18 months or so....