I would imagine that your Mac Pro is still faster than a comparably clocked late 2009 Quad iMac. If you need a faster graphics card, then you can pop one in and go. That's one of the advantages of having a Mac Pro. I don't understand why someone feels "mugged" when a newer computer comes out for less money than what they bought. That is the basic reality of buying anything based on technology - there is always a newer, better one around the corner. In fact, the day Apple launched the 2009 Mac Pro they were already developing the 2010 Mac Pro.
The entire iMac line was Core 2 Duo at the time 2009 Mac Pro was introduced with 4 and 8 cores. iMac always gets the Mac Pro hand-me-downs, so it was inevitable that a 4-core iMac would hit the market later in 2009. We will most likely have 6 and 12 core Mac Pros by March of 2010, how will you feel then? Murdered?
Those who buy a certain computer for bragging rights or vanity will always feel emotionally mugged when a new machine comes out. That's because they have invested themselves emotionally into a piece of hardware that is obsolete, therefore what they have invested emotionally into having "the best and fastest" is now lost to the next generation. A typical mourning process ensues over this loss. Those of us who use our computer to generate income couldn't care less about what is coming out or what's coming out in 6 months or next year. We depend on our computers for income, and invest appropriately. I look at my 2009 Mac Pro purchase as one of the best investments I've ever made. It's increased my productivity, gives me access to certain tools via VMWare that are only available on Windows, and ultimately has played a key role in increasing my revenue this year. Buying it when I did was an absolute necessity, and it has paid for itself many times over.
I also built a VOIP PBX system for my office using a Mac Mini running Linux. The Mac Mini is 2 years old and runs Linux under VMWare. This $700 investment has saved me thousands of dollars in what I would have otherwise spent on a commercial off-the-shelf PBX solution plus all the money saved on not paying exorbitant fees to the phone company for multiple lines, per minute charges, etc. New Mac Minis have come and gone in the meantime, but do I care? The one I have is working great for its intended use, saves me money every day, backs itself up to a network NVS using Time Machine, and one day when the hard drive fails I'll pop in a SSD and reinstall everything from the backup. I'll be up and running again within a couple of hours, and faster than before.
If you look at your Mac as a necessary business investment, you're less likely to be inflamed by newer iMacs and Mac Pros. Keep it real folks. Don't put your heart and soul into plastic, aluminum, and silicon. Save that for your family, friends, and career.