I have been looking at a new iMac loaded up with a the fastest processor available, plenty of RAM, SSD drive and a 1 or 2 TB second drive. That prices out at a little over $3,000, which is acceptable. I think the iMac would have adequate power, but the monitor would be ok but not ideal in terms of accurate color.
Just for grins, I went to the Hewlett Packard web site and configured an HP desktop more-or-less like the iMac I have been looking our. It priced out just under $2,000, which means I could add the wide gamut NEC monitor and still be within my budget. . . .
So the questions is, for purposes of image processing, would it be worth migrating to a Windows-based system to gain the advantage of the wide gamut NEC monitor?
As others have pointed out, at any given price-point you can get better processor specs with a machine designed for MS-Windows that you can with a Mac.
Having said that, if you want to stick with Apple hardware, it's fairly clear to me from some monitoring I have done on my own machines that the performance constraint which most affects both Lightroom and Photoshop on Apple's OS X is the speed of demand-paging: how fast the operating system can move data between solid state memory and a disk ("swap" space), rather than anything to do with image processing, per se. In other words, I think it's the large size of the image datasets that is most likely to slow things down. I'm not claiming that you can't
run out of CPU when working with Lightroom and Photoshop, but I think that's not likely to be the problem on any recent desktop Mac. Some people with credible UNIX and Linux backgrounds believe OS X's memory management is broken. I'm inclined to agree that it's not up to the standards of other *NIX variants I have used.
Having sufficient unallocated RAM seems to dramatically alleviate the symptoms, however. With enough free memory, it doesn't matter how badly the OS X kernel manages it. There are pretty severe limits to how much RAM you can stuff in a current iMac or Mac Mini. However, both of those desktop systems, as well as the Mac Pro, are due for product refreshes before the end of the year. I have no inside information, and there are some power and heat dissipation restrictions on how much memory the smaller Macs can reasonably absorb. Using third-party upgrades, I believe the current limits are 16 GB for a Mini and 32 GB for an iMac. However, I am quite confident the next generation of both systems will have improved specs—my guess would be 32 GB for a Mini and 64 GB for an iMac. (Although you might have to use a third-party upgrade to reach the real limit. Apple is rather conservative about how much RAM it will support in a small machine, probably out of concern for overheating.)
So how much RAM do you need? I haven't done any rigorous tests, but my instinct—and I've done a lot
of performance tuning of UNIX systems over the years—is that a good metric would be a minimum of 8 GB per CPU core. That seems to be a reasonable but not excessive amount of RAM to make available to each hardware processor on a 64-bit machine, although you might need to go as high as 16 GB/core before you reached the point of dramatically diminishing returns.
Again, as others have said in their responses to this thread, for any given price you can buy or build a faster box to run MS-Windows. If you don't mind spending most of your time in post in a Windows environment, that might be a reasonable alternative. As much as Apple pisses me off at times, that's a non-starter for me, but your mileage may vary; I believe it was Jeff Schewe who said recently in one of these forums that current versions of Windows don't suck as much as earlier ones.
On the other hand, if you want to stick with OS X, my recommendation would be to hang on for a while. I suspect the next generation of Apple desktop products may well be interesting.