Where's the Bottleneck in Exporting, Also Slow to Launch?

Hi all,

I have a fairly powerful computer, an 8-Core 2.8GHz Mac Pro (Early 2008) with the NVIDIA GeForce 8800 GT, 4GB of RAM (4x1GB), a 750GB Western Digital 7200 RPM HD as the boot drive (swapped from my old Dual 2.0GHz G5, so it's still APM formatted), and the stock Seagate 320GB drive in bay 2, all running Leopard 10.5.6. The thing that still frustrates me is the speed at which Aperture exports photos. Granted, it's light-years faster than the G5 was, but it's still not fast by any stretch of the imagination. I regularly export scaled down JPEG's for uploading to the web, and all my masters are 10 MP Nikon D80 RAW files with various adjustments. I batch apply exposure recovery, enhanced saturation, definition, and vibrancy, and sharpening to all photos, regardless of any other adjustments. I try to use shadows/highlights sparingly, since I know that can double the export time, but this isn't the root of the question.

What I'm really curious about is, where is the bottleneck in the export process? It seems that something isn't working as fast as it could, because although Aperture uses all 8 cores during export, they're never close to maxed out. For example, if I export a series of photos to JPEG at a reduced pixel size, all cores will crunch at 70-80%, with Activity Monitor reporting Aperture at about 540-590%. At work I have the same generation computer, except it's the 4-core model with the Radeon HD 2600 XT, and the cores get just a little closer to max, with Aperture using around 300% of the CPU. Interestingly, if I export JPEG's but at the original size, the processor cores fluctuate between 400% and 600%, although the total time is pretty much the same.

The processor cores clearly aren't being utilized to their maximum potential, so where's the holdup? There's very little disk I/O during all this, so I doubt that's where the problem is. While doing these tests I had about 800 MB of free RAM, so the amount of available memory doesn't look like an issue either. The 8800 GT is a great video card, but I don't know of any way to measure its involvement in this. The only other thing I can think of is memory bandwidth. Even though I'm not really running out of RAM, could filling all the RAM slots pump more data through for the processors to crunch? If memory is the bottleneck, I could go from 4 to 8 GB, but it's actually quite a bit less expensive to get 2x2GB instead of 4x1GB. Would going with the 2GB modules and leaving 2 slots free not give the same benefit as filling them all? Or maybe Aperture is just way too dependent on the GPU (which is true), and that's the root of the issue. Any thoughts?

The other question has to to with launch time. With an empty library, Aperture opens up in just a few seconds. My library has 25,000 images, and it takes a good 20+ seconds before it's ready to go. I've tried all-managed and all-referenced masters, and that doesn't seem to make much difference. I've rebuilt the library, and tried the SqLite database optimization, and those didn't really make much difference either. It seems other people don't have this problem, or maybe they just don't think 20 seconds is too long, but are there any other ideas? Is there some way I can better use that second hard drive to help with this? Right now I'm just using it for some dead storage. I already went to two separate libraries, and while it does seem to help some, it's annoying to switch and I'm already running into situations where I want to use pictures in both libraries.

Thanks.