I've just upgrade my old 8-core 2.26 GHz mac pro to use a new pair of x5570. Thats means now i've own a mac that once time its cost 5,899 USD!!!!! Form my experience i want to share 5 things. 1.) I've using 2.1 mm of washer (0.7mm x 3), and it work great!! you just tighten the screw and it set, no fan problem ho heat problem. (Idle 44c under Ambient 39c very hot in Thailand) 2.) I doesn't adjust, modify fan connector just use it as it come. 3.) I've add 2mm thermal pad to my heatsink, Add from pink thermal pad. 4.) It's very very easy. Doesn't need to hesitate. 5.) About the processor. - I choose x5570 over 6-core variant because it much cheaper.I've paid just $380 for two of these. (vs $400 for just one of 6-core 2.4GHz that much lower frequency) - I choose x5570 over w5590. Because it TDP is 95watt, follow Apple specification, I know w5590 can use without problem in 2009 pro. but my home is very very hot so i think i need lower TDP than +0.3 GHz max frequency. - Another thing is about my dream, in 2009 I've dream to own the most expensive mac money can buy (8x2.93 Nehalem). That time i can't do. Today it very affordable to do.Why not?