Upgrading power5 p595s to power6+ 5Ghz ,power 595s (9119-FHA http://publib.boulder.ibm.com/infocenter/powersys/v3r1m5/index.jsp?topic=/iphdx/595_fha_landing.htm ) has got to be a great bang for buck upgrade.
P595's have no end of life against them yet and the power6+ processor books have dropped in price almost 50% (eg http://www.theregister.co.uk/2010/03/18/ibm_power_595_cuts ) and a 64 core p595 upgraded with 5GHz p6+'s is about as powerful as a new power7 3.5Ghz 64 core p770
System Name SPECint_rate20063 SPECfp_rate2006
IBM Power 595 2160 2180
IBM Power 770 2013 1689
(so you can still consolidate a lot more eggs into the same basket if thats your aim) and p595 has better RAS eg no single p5ioc chip handling both GX++ ports ie loosing the wron p5ioc kills all IO on the CEC - this was the case with the p570's too)
power6+ can do all the multiple shared pools(oracle savings), VIO, AIX6.1, WPAR, live partition mobility, micropatitoning, active memory sharing (not active memory expansion(Trade CPU for RAM) or max/turbo/intelli core that all sound a bit multimedia cdrom come MMX technology to me)
p595s can be upgraded to power 595s with just new power6+ books - no need to change anything else its what Auspost did - just by adding the new power6+ books you can free up lots of space (consolidating) and gain all of the good power7 features without increasing your footprint 1RU https://www.ibm.com/developerworks/aix/library/au-upgrade_power6/ (Chris Gibsons experience)