After working in computers, both personal, and business machines, I've found building a computer from the ground up is the best way to go for using a computer for a specific purpose.
Just the power supply on a computer takes a beating over the years. Off the shelf computers have a power supply that is specified for only the amount of power the entire system will draw when running. The selection of that PS should give at least 50% greater power than the power the computer will use. This rating is in amps, mili amps. If the mother board is rated to draw 1 amp, be sure the PS can produce 2 amps. Any electronic device will only draw the amount it needs to operate, so the mother board will be easy on your PS by only drawing 1 amp. Be sure the voltage is correct for the mother board though, higher, unregulated voltage will kill your computer. This usually what happens when the computer just dies. The regulators in the power supply break down and allow voltage fluctuation into the system, and it kills the processor, ram, and even motors for hard drives.

Your mother board should be professional quality, not consumer. It should have the fastest processor available, but professional. The mother board should have onboard ram slots for twice the amount normally found on consumer grade computers, and the ram arrays should be professional quality. You are building a professional high speed reliable computer.

Hard drives should be professional quality, with high speed run speeds. These hard drives will be above or at 1-10 tera-bites.

Video should be professional quality, with a processor built in, and as much ram as possible. Don't forget your monitor. I should be able to be easily calibrated, and be a suitable size. Multiple monitors would be best.

Don't forget to buy a suitable regulated battery backup power supply, that will power your computer for at least 30 minutes. This will allow you, should a line power failure, or brown out occur to power down your computer properly.

The budget for this system would be about $4-5000.00. But, if your incorporated is totally deductible as long as it is used for your photography business.

Hi FrumCA, I've forgotten that point, and it is a valid one. When I switched, I had to pay Adobe some kind of platform fee to get the Mac version since I originally paid for the PC version. The same will probably be true for Microsoft Office, for I use the Microsoft Office for the Mac. But this will be a one time fee.

Let me leave with this thought. Every morning, when we leave for the day, I don't expect to ""have to fix our cars"" just in order to drive them. Certainly not daily. Yet, that is what was happening ... all the time ... with my PC's. Doesn't happen any more with the Mac. That, alone, would make it worth while to pay the price of buying switched-platform software to switch to the Mac. What price can you put on a good night's sleep?