I don't own that kind of a setup, but judging from the pics and knowing how tall the heat spreaders are on the vengeances, I would say that you will have issues putting RAM into the first bank. Because that fan assembly comes quite low, basically below the fins of the heatsink. You 'should' be ok with the 2nd and 4th bank for dual channel installation though.
Considering the size of the HAF X, you might want to get an extension cable for the 8 pin MB connector so you can route the cable properly behind the MB tray.8" extension12" extension
Can't really tell what the deal is with the fans, maybe someone has a HAF X case and can tell what connectors the fans come with ( 3 or 4 pin )