For mw12a and others...
...They key to my setup is that I use the trading PC only for trading. I don't even run a browser on it. No anti-virus, no email, no IM, no web browser. Just the programs I need to trade. That reduces the chances of another program competing for system resources, and also minimizes the risk of getting a virus. A lean and mean dedicated trading machine.
I use my Mac Pro for everything else, including market research, etc. Keep it all off your trading PC.
With this setup, my trading PC can easily handle busy market times - CPU rarely get's above 30%, and my memory usage is a constant 1GB. I run Tradestation, Ninjatrader, and sometimes Interactive Broker's TWS, along with two data feeds. Network bandwidth hits 1-2Mbps during market open and close, but usually only for a minute or so. More importantly, my PC remains responsive at all times.
So bottom line advice is this - get a quad core PC with 4GB memory and a dual-DVI video card (get a cheap one, you don't need much power, we're not playing video games). Put a clean install of Windows 7 on it, and only install the programs you need for trading. Get two of the biggest (resolution-wise, not size-wise) monitors you can afford. Screen real estate is everything.
Then get a third monitor and hook it up to one of your mac laptops (or get a mac mini), and use that for all of your non-trading stuff, including market research, excel spreadsheets, etc....
...Let me know if you need more specific recommendations.
mw12a and others, I totally get that it is a compromise to use a Mac in the business of trading to run some or part of your operation. I get that there are self-imposed limitations in terms of choice of applications to run by choosing to use a Mac. Lets put it this way, there are very likely no/zero diehard Windows users out there who are looking to setup a trading operation who are saying to themselves that in order to do so, they need to leave Windows, learn the Mac OS and get a Mac! This isnt happening. Some of us here, are probably former Windows users who are happy with the switch from Windows to Mac and are trying not to have to go backward to Windows if we can help it. Thats me. If I choose to use applications that are Mac based then there isnt much of a compromise provided that I am happy with the applications. However, I havent made those decisions yet.
However, for the moment, lets table the idea of running an entire trading and analytics operation on a Mac-only platform. Lets explore the idea of a hybrid Windows and Mac setup such as what was mentioned above.
I suppose, one could run a trading operation on a lean, fast PC running Windows 7 64-bit with multiple monitors and 8GB of RAM (yes, I heard all of you! 8GB not 16GB
thanks!

. On that system, you can run eSignal, TradeStation, MetaStock and other Windows only based programs. For me, it is feasible to have my MacBook Pro with 4GB of RAM running another external monitor and putting analytics on it. Research can be done on it, etc. On one of my MacBook Pros I have Vista running in a BootCamp partition. I could hook up another monitor (I hope Vista will allow that) and run either eSignal, MetaStock or Worden Bros. on it. On a MacPro I could run Snow Leopard and run IB or thinkorswim, basically the trading platform.
What I am gleaning about the best and most cost effective MacPro configuration is that it would have an i5 or i7 processor (I would go for the i7, you get 4 fast cores from the get-go), 8GB RAM, a moderate sized hard drive or solid state drive, possibly a RAID array with no striping. You would have as many video cards as you need monitors but they dont have to be high end since we are not doing CAD, video, and gaming. We also want the fast incoming internet connection available. The monitors should have the best resolution, but not necessarily be the largest in terms of dimension. So far so good? Switching gears
My question about having a hybrid setup is this: Do you every have to share data between the trading platform on the PC and perhaps Office applications running on the Mac? Since, your operation is split between two computers and you arent running email or a browser on the PC how are you moving or sharing data between the two? Is it ever necessary to do so?
I am interested in mw12as answer to that. I welcome everyone elses answer to that, as well. But pending receipt of those, I would think that if you are getting a PC, then just have your whole operation on the PC. What advantage could there be to the hybrid system? On the other hand, if you wanted to be Mac OS-based then there would be the pull to have some Windows functionality, just because there are more programs for Windows than Mac in terms of trading, charting and analytics. That would have to be done, practically, speaking in a virtual machine with Fusion 3 or Parallels 5. How well it can be done, I dont know. What I would do, if I was to go this route, is to make a BootCamp partition, install Windows 7 64-bit on it and then install Fusion or Parallels. That way, during market hours I can run my Windows applications in the virtual machine. If I am working after hours, I can use BootCamp to boot into Windows and run the same applications natively in Windows.
Alternatively, I could leave Windows off the MacPro and run all my Windows non-trade execution software on my MacBook Pro running Windows natively from its BootCamp partition plus/minus an external monitor.
I hope that wasnt confusing. All comments and discussion appreciated.