I originally built this computer with the Asus M2n32 Sli Deluxe board and the AMD FX-62 chip. 

It has always been a source of pride to have that FX-62, and I was never interested in upgrading (especially due to the $900 price tag for JUST that CPU when I originally bought it some years ago).

But it's been clear that I needed a bump in processor cores/speed lately.  Have been having trouble keeping up with large 1080p bluray files (ringing in at sometimes 12 to 20GB a peice); getting bogged down and sync out issues every now and then.  

I started the upgrade looking for a full i7 955 setup.. nevermind, that was going to ring in at over $1900 for all the pieces I would need in the end.

Then showed up in my search results, the AMD Phenom II X4 940 Black chip (for a mere $150 on Amazon.com).  Made for AM2+ boards, and guess what? Yep, it fits and works just happily in the AM2 boards too!  Just need to make sure you have the latest BIOS.

Arrived in UPS this afternoon; installed 10 minutes later; overclocked by 10%; everything is just SCREAMing along now.

I don't like benchmarking tools, they rarely mean anything to me.  So I just tested the programs/games that I use every day.  Sorry, this isn't going to be scientific.

A few numbers:
The FX-62 was running stock at 2.8GHz dual core.  The 940 is at 3.3GHz quad core. 
Graphics card is GTX260, memory is 4GB DDR2 800(3.5 registering in Win7 Pro x86)(unganged mode now with the Phenom II X4 940).

Mass Effect 2 on FX-62 took 45 seconds to go from desktop to resumed game, and maybe 5 to 10 seconds between the various levels of the Normandy ship.  Framerates not recorded, but always smooth as glass.
Mass Effect 2 on Phenom II X4 940 takes 8 seconds from desktop to resumed game, and <1 second between the Normandy ship levels.  Framerates still smooth as glass.

Sims 3 on FX-62 took 4 minutes from desktop to loaded game of one family of 5 in a large lot, fully built out and landscaped.  Framerates not recorded, but were slightly stuttery now and then, I would guess ranging between 25 and 40 depending on the area.
Sims 3 on Phenom II X4 940 takes 2 minutes for the same scenario.  Framerates improved noticeably.

Dragon Age: Origins on FX-62 took took 5 minutes from desktop to loaded game (mid game save point, 3 party members, mid-quest).  Framerates were 40-50.
Dragon Age: Origins on Phenom II X4 940 takes 1 minute for the same scenario. Framerates are 50-70.

Roller Coaster Tycoon 3 (don't laugh it's rad!) on FX-62 took 2 minutes to load a custom scenario of biggest land available, fully terraformed, fully themeparked, fully active with ~2700 guests.  When in live mode, framerates were down in the low 20s, 15s at nighttime.
Roller Coaster Tycoon 3 on Phenom II X4 940 took 1.5 minutes to load same scenario.  Framerates are now at 70 day, 50 night in live mode.. woah.

Photoshop CS4 doesn't really benefit from quadcores that I know of, but the clockspeed turned my test run of a 4000x4000px@300dpi photo with Fractalius Glow 100 showed a reduced render time of about 10 seconds from the FX-62 run on that same photo.  Not shabby at all.

Playing huge gigabyte bluray MKV files doesn't even ping the process explorers cpu graph now.  That used to be maxed out on the FX62.  Excellent!

So, if you're considering grabbing that last possible CPU upgrade on your old AM2 board, I would totally stand behind the Phenom II X4 940 Black chip.   Most excellent.