Optimize workbook performance - excel keeps thinking and crashing

Hi, I have a workbook containing 12 sheets. There is a lot of cross-referencing between those tables. There are 3 external linked files, but the data from there is fairly static, and it's 'one way traffic'.

There are quite a bunch of lengthy formulas that are copied down a few-thousand lines. I abstained from using any range formulas or 'indirect' functions and such. Formatting is also very limited. There are only a few columns containing conditional formatting rules and there is basic color coding of most cells. No VBA.

All in all the sheet is 11MB and I run it from a local server. This seems to be fairly innocent from my point of view. When records are dealt with they are pasted as values, so only some 1/3rd of about 10,000 lines, spread over 50 columns contain formulas, some simpler than others but nothing fancy.

The simplest copy-paste actions over 40 cells can take excel 10+ seconds to deal with and often crash all together. I have cleaned up formatting in this workbook, removed unnecessary external links and gone over all formulas to simplify or remove where possible. On that last point; there are a LOT of dependencies over all these sheets but the formulas are merely simple sumifs, index-matches, vlookups and IF statements. I do rely on auto calculation. I turned it off but to the effect I had to calculate the sheet after every action with the same effect (which indicates the connection to other sheets or calculation thereof isn't the problem)

I've gone so far as to get myself a new computer to solve this:

Chipset: Intel C226 Chipset
CPU: Intel i7-4790-3.6G 8M GT2 4 Cores 8 thread CPU
MM: 16 GB DDR3-1600 nECC, 4GBx4
2*1 TB 7200 RPM SATA hard disk, support raid 0, 1

The problems are the same, whether I run the workbook from its server location or copy it to my computer locally.

I am completely lost what remains to be done. Simple copy-pastes of a few cells can crash excel while I often copy down 50 columns of formulas down 200 lines without too much hassle. ANY suggestions are welcome. Does anyone know of some diagnostic tools that trace excel inefficiencies? I can imagine that my Workbook is still harbouring a culprit. I've done everything but checking cell-by-cell for some rogue issue.

I'm sure excel has its limitations but I refuse to believe I've met the roof on a 50,000 cell, 11 MB workbook.

Anything, Anybody???

I had similar problems. I turned to VBA to do most of the calculations and present most of the calculated data as numbers.