I'm an advanced amateur/hobbyist photographer using PS CS3 & Lightroom (often open at the same time) with a G5 dual-core 2.0Ghz (last revision) and 4.5 GB RAM. I have OS X system & apps on a 74 GB Raptor boot drive and user directory and images on a 750 GB SE2 internal drive. I backup to an external FW 400 GB drive. PS scratch is currently set to the 750 GB SE 2 drive, which is about 30% full.

I'm debating about whether to upgrade to a Mac Pro when the new Penryn models are rumored to come out in January, or whether to spend less and simply upgrade my existing system.

My question is, what could I do (if anything) to significantly improve the performance of PS CS3 & Lightroom on my system? I've considered using the 750 GB SE 2 internal drive as a scratch disk, and then buying an external enclosure that would contain a RAID 0 volume (750 GB SE2 x 2) for image files and 2 750 GB SE 2 single drives for backup. I would also boost the RAM to 8-10 GB.

Of course all of this would cost me something like $1500. If I sold my G5, and ended up buying a Mac Pro & configuring it accordingly, I'd end up spending about $2500-2750 ($3500 minus $1000 for the G5).

Do you think I'd see much improvement at all in my current system with the changes I'm considering above? If not, what would be the most performance and cost-effective way to upgrade my current system? Or should I just spend the extra $1000 and get a Mac Pro?