I upgraded my 1,1 with a couple 5160s for FREE. That was cost after selling my DUal 2.66s. I still toss around idea of adding 5365s but now getting 5580/90s for my 2009 has moved higher in the priority list. (for many apps, the "old" Quad 3.0 is quicker than the "new" Octo 2.26). Unless you have an app that can use more than 4 cores, (or Grand Central ever starts doing what it was hyped to) you will get much better results from fewer cores at higher speeds, at least for the Krone spent.
BTW, as you are in Denmark. Are you a fan of KiMs? I was Art Director for live action part of approx 10 of their commercials over past 4 years. My fave was the 10% spot where we made Jorgen into a rapper. I enjoyed the crackers but wasn't super fond of the actual chips. I used to do the "Nordea" spots but they switched ad agencies a couple years back. One of my best sets, a huge snowy Alpine hillside was shot here in sunny SoCal but due to ad agency mess, the spot never finished post and all I got was a few pix with snow and a giant green screen where mountains were supposed to go. Oh well....