Since OP hasn't responded, I just created a new spreadsheet with adjusted price for 27inch model as I described in the quote.
Click here to see the Updated Spreadsheet with few more columns(adjusted price for 27inch and education pricing)
And for the (geekbench score / price) ratio, I have added two more columns that might be interesting to some readers here.
1. Performance / Adj. Price - Ratio column:
Same as what OP did but instead, I divided it by the adjusted price(which is same for all 21.5 inch models, 200 less for 27 inch models)
2. Education discount with iPod touch value calculated as 160 column:
This is for ppl who are looking to buy with education discount. When i calculated the price I subtracted 160 more from education discount(-200 more ontop if 27inch model)
Also, I fixed the minor errors in pricing as OP had $1679 for i5 - 3,6Ghz (corrected to 1699) and $2179 for i7 - 2,93Ghz(corrected to 2199)
As we can see on the table, for new 2010 iMacs, the 21.5 base model and 27inch i7 is giving the biggest bang for your buck.
Obviously, the 21.5 base model dominates more for education pricing ( 5.76 vs 5.41 GeekScore/dollar)
Refurb i7 definitely stands out... it would really stand out if they gave iPod touch for refurbs..
However, if you have dollars to spend and access to education pricing, i guess new iMacs(only base 21.5 and core i7 27inch model) aren't bad at all, as their score/dollar values look pretty comparable to those of refurbs. After all refurbs aren't exactly new. (Although some of them might be new as apple may be busy burning the previous generation stock

)
BTW, the reason why i only subtracted 160 for 200 dollar ipod touch is that i figured many people will sell it on ebay around 170 ~ 180 + shipping then there are fee that ebay charges and paypal charges(EVIL!!!!

) so that's why it's 160.