Just wanted to weigh in a few thoughts. First let me answer something others haven't for you yet... I have been doing a lot of research on 1 series bodies because I am still trying to determine if I am better off with one of them over the 5D2 I just got.
AFMA - 5D2 and 1DIII both have AFMA adjustment. 1DsII *does not*
LCD on back - 5D2 and 1DIII both have nice, larger LCDs and sport the newer menu systems. 1DsII has a much smaller LCD and uses the older 20D/30D menu systems without tabs where you have to scroll/jump through one LONG menu.
Batteries - 5D2 uses LP-E6 which is a very popular and common battery (used in 5D2, 5D3, 6D, 7D) and a few others. 1DIII uses a NiMH or Lithium (forget which) battery without the 'memory' problems of NiCad as found in the 1DsII - which BTW is a much larger and heavier battery with less capacity.
Mode switching - While I have not used the 1DsII body, I have read that it is cumbersome to switch between various shooting modes, etc.
You should read the TDP review on the 1DIII - it describes all the things that improved or changed for the 1DIII from the 1DsII. http://www.the-digital-picture.com/Reviews/Canon-EOS-1D-Mark-III-Digital-SLR-Camera-Review.aspx
I presently own a 5D3 as my primary and have owned a 5D2 and just purchased a 5D2 refurbished from Canon Direct - they are $1,495. You didn't let us know how much you could get that 5D2 for, but the fact that it is lacking the filter/is equipped for IR, may be more of a burden than anything esp. for resale value.
If you are looking to shoot wildlife and/or sports subjects, between these cameras, the 1DIII hands down. Otherwise, if lower-light and high-resolution portraiture is your subject, then 5D2.