Going to buy first iMac

You'll be missing 500MHz on each core and 4 Threads. So roughly twice as slow. The iMac i5 is 4x2.5GHz, you have 8x3.06GHz. So quite the downgrade. The 6870 you have wipes the floor with even the 6970m in the top end 27" iMac. Your Samsung F3 is a bit faster than whatever stock HDD they plop in as well. At least you know it will be a downgrade. On the plus side you are upgrading your OS and apps and if you were not using the full HW potential of your PC you may not miss it.

 

Don't worry about the processor difference. I've seen many i5 vs i7 comparison and the difference isn't huge. It would only matter if you had huge rendering tasks to do as usually the i7 would save you 30 seconds of exporting time on something that normally takes 5 minutes to export. So this wouldn't be the biggest downgrade. For the graphics card, although it would be quite a downgrade the one in the base model iMac is still decent. I say this from fact as my dad has the 2011 base model iMac and it plays cod4, battlefield 2 and assassin creed brotherhood very smoothly and they are all ported version too. Obviously it might not be good enough though if you want to play some of the top latest games through bootcamp but it's still good enough for most game and 3D modeling (I have used Maya 2010 on it). Hope that helps

 

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I would have said get the 27" iMac with the 3.4ghz quad-core i7 and the 2GB 6970. And as for the RAM swap the one from your old pc onto the iMac and put the iMac RAM inside your old pc (if you plan to sell it) then you won't have so much of a downgrade.

 

If you use the PC for games stay put with what you have otherwise you will be disappointed.

 

Some numbers. And as mentioned by other poster. NOT twice as slow. I was incorrect. Expect this on Geekbench.
i5 @2.5GHz: 7185
i7-940 @2.93GHz: 9268

Your i7-950 would do slightly higher (100-200 or so). Real world may not even notice as it depends on your tasks.

 

If gaming is the number 1 thing you use your computer for then really the only apple product capable to run the latest games at max detail settings and resolution settings is the monster mac pro tower.

And the core i5 sandy bridge cpu's are equal or better than the core i7 9xx x58 chip set cpu's in almost all computing tasks. The only situation where core i5 SNB loses is vs a 6 core gulftown with HT in a heavily multi-threaded workload and that's only cause its 4x threads being processed vs 12x threads being processed at once. SNB is faster at the same clock speed and also has superior single threaded performance. So basically each thread on sandy bridge can process more work then each thread in gulftown. And clock for clock SNB processes more work than x58. It's just a better architecture. Does more per clock and more work per thread vs previous gen

 

Not true. Max resolution of 2560x1440 yes. Nothing Apple sells does that even though it is their favorite res.

Wrong. So wrong. i5? Dude, the i7-980x will trample most of the i5's in single threads as they throttle to 3.6GHz. On multi it is no contest and i7-2600K can't beat i7-980x. SB architecture is more efficient but most of the gains are purely because of the turbo headroom being raised 1x higher.

 

They're not the same so you can't.