SumIf The Sum Of Unique Values Is Greater Than Criteria

I have a problem which is beyond my capabilities. I need excel to sum amount column (See example table below) by unique values in company column then conditionally sum those values based on the year of investment, stage of company and finally, the kicker, the summed Amount by unique companies value has to be less than a certain threshold.

For example, I want companies in Stage Column of Exit only and in year 2004 only BUT only if the sum of the Amounts by unique company values is less than 100. So in the example table this would return 0. I have code and criteria written to sum unique values based on similar criteria such as sum if company Stage is Seed and Year is 2004 but for the life of me I can't seem to make the jump further.

For Unique values I used this function:
=SUMPRODUCT(($B$2:$B2=Year04)*($D$2:$D2=StageS)*($A$2:$A2=$A2))=1
Then:
=DCOUNTA($A$1:$D9999,2, Criteria)
or
=DSUM($A$1:$D9999,2, Criteria)

This along with criteria explained before returns the number of unique companies that are Stage=Seed and Year=2004 or sum of amounts with that criteria.

I am trying to adapt this technique to get what I want but to this point have been unsuccessful. My best guess is that I will need to create an array of the unique companies (New Sheet column A) with the Summed Amounts (New sheet column B) and then run functions again with the easier equations and criteria? I am trying to avoid combining company records as each investment needs to remain individual and there are 16000 records. Any help would be greatly appreciated.

Company Year Amount Stage XYZ 2004 10 Seed XYZ 2004 20 Seed ABC 2004 5 Early ABC 2004 25 Early DEV 2004 14 Later DEV 2004 19 Later TRU 2004 100 Exit TRU 2004 120 Exit TRU 2004 100 Exit