Hi Calaudude,
I paid £700 for the original machine and it was spec'd at 2x E5-2640, 64GB RAM, K4000 and 2TB HDD. What I received was 1x E5-2660 (and no 2nd CPU riser), 32GB RAM (PC3-12800R), K4000 and 1TB HDD. However the seller supplied the 2nd CPU riser, additional E5-2660, and 32GB RAM (PC3-14900R) and 2TB HDD.
I got my K4200 for £275 on ebay but sold the K4000 for £225! So£50
Sold the 32GB PC3-12800R for £80 and bought another 32GB PC3-14900R for £100. So £20
Sold the 2x E5-2660 for £85 and bought 2x E5-2670 for £125. So £40
I think you get the general idea. The 2-port SATA III PCIe card (also has 2 ext. USB3 ports) cost under £15, ICY dock £35, 4TB drive £100, 256GB SM951 £60, ASUS Hyper Mini PCIe card £16, SanDisk 480GB SSD £85.
The Tesla project was by far my biggest budget item to date coming in at £230 but still better than paying £1200+ for a K6000.
Total spend so far I suppose is at the £1350 mark. I generally get good deals by searching out the bargains on ebay or gumtree.