I've got Athlon 6000 x2 and 8800 GT and this PSU:

 http://www.newegg.com/Product/Product.aspx?Item=N82E16817194003

 It's got 22 amps across both 12Vs and it pulls my setup flawlessly.

 Now for SLI setup I'm looking for something with at least 3 12Vs and at least 20 amps across all of them.  Can anybody recommend something good?  I can't seem to find anything...

 

 

Well it all depends on how much you are willing to spend. OCZ makes some damn good supplies and if you are looking for one of the best I would suggest this one  . But like i said, it all depends on how much you are willing to spend. The PSU I linked should last you awhile and it has 4 12 rails @ 20amps accross each and over 1K Watts.

I've tried a number of different PSUs and have become a big fan of Corsair products. You can get a great 620W modular (and very quiet) power supply with this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16817139002

or for a more powerful (but not modular) 750W PSU, try this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16817139006

Both are SLI ready. I personally use the 620W model because it's modular and a great PSU, but the non-modular PSUs from Corsair are just as good and a bit easier on the wallet. You really can't go wrong with Corsair. Hope this helps.

Laggerzero - that PSU is really nice, but the 4th 12v is an overkill in my case

Redline- the first PSU is too weak, but the second one.. that's the weirdest one I've ever seen.

 

Only one 12V, but SLI certified, and it has 60 amps on that rail... 60 AMPS!!  I've never seen something like that.  Is it better to have one 12V with 60 amps or 3 12V with 20 amps each? 

Both PSUs I mentioned are SLI certified. Trust me, the Corsair 620W works just fine - It's what I use and I love it. It runs 50 amps combined on 3 rails and even the description says "The CORSAIR CMPSU-620HX power supply has gone through a series of rigorous NVIDIA SLI certification tests for maximum system stability when building NVIDIA SLI PCs."

Regarding the second PSU I mentioned (CORSAIR CMPSU-750TX 750W), it's a nice one and does pack 60 amps on a single rail. The benefit is that the PSU auto-adjusts to allocate power where needed. When the amps are spread out over multiple rails, you have to balance the load yourself to make sure everything gets enough power. I've used both and find the single rail is a good way to go for those with minimal building experience or anyone just not interested in spending much time worrying about power requirements. Mostly, single vs. multiple rails is a user preference issue and there are benefits to both. You could fill a whole forum discussing this topic because you'll get a lot of arguments for both sides! 

 For an 8800GT SLI setup, the minimum recommened PSU is a 450W w/ 28A 12V rail. Your current PSU should be able to handle it just fine. I have an Antec SmartPower 2.0 500W running an SLI setup flawlessly.

 A good choice would be a PC Power & Cooling Silencer 610.

You might take a look at BFG just open a ne website dedicated to power supplies and recommendations for possible configurations to the customers setup! see it here:  http://www.bfgpower.com/