I think it might mount ok (it appears to be an Asetek clone):

http://www.tweaktown.com/news/18558/asetek_and_antec_team_for_kuhler_h2o_620_cpu_cooler/index.html

and pretty sure 620 and 920 mount the same way. This user got after-market Asetek clone to attach ok.

http://en.community.dell.com/owners-club/alienware/f/3746/p/19375026/19860709.aspx#19860709

just watch your case to radiator mount space. Might have to mod the case a bit to get it to attach in that space.

I think your only problem will be controlling it. If you want to convert back to MIO-Board control, you can reference this:

http://en.community.dell.com/owners-club/alienware/f/3746/p/19454479/20130266.aspx#20130266

Pretty sure the Corsair H50 is the match to ours (but you still need to re-wire). While newer ones "look" the same, they are likely electrically different (the digital controller part). Or, just use the Antec way (like it was installed into a more normal computer) but then it won't appear in Command Center with others.

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All that said, it would be easier to just buy a new one from Dell spare parts. Note that the one for the Aurora is different than the Area-51 part. I would NOT buy used.

EDITED (added more details).

i just put a h75 corsair in my r6.  i used both fans.  Installed top fan and radiator first then installed the bottom fan.