When I see all of the requirements that you list, it seems as if iPhoto would be absolutely perfect for you, with no shortcomings whatsoever. Yet you specifically say that you will not accept iPhoto as a solution. That is surprising to me.
I have 33,000 images on my iPhoto, all large RAW files, and it works wonderfully fast and easily, despite the fact that my computer is very under-powered with only 1 gig of memory. All other programs on my computer - Aperture, LightRoom, and Photoshop - are painfully slow. But iPhoto is blazingly fast, despite the huge amount of data I have fed it. Full screen/large window image views are generated rapidly, allowing me to go thru 1,000s of images quickly.
Might I ask why you choose not to use iPhoto for the tasks you need to perform? What, specifically is the shortcoming?
Do you have all 33K photos in iPhoto on your internal hard drive? I had 14K photos (all JPEG) on my 4GB 2.4 HGz Intel Core 2 Duo MBPro and iPhoto gave me the spinning wheel. Maybe it was due to my 250 GB being almost full and not the iPhoto program?
Now that I have all my images on an external hd it would make sense to import them back into iPhoto 1 year at a time so I can sort through them in smaller batches.