Speaking of those aftermarket cooling units:
1) They do this mainly so they can lock certain models into only working with certain GPU or motherboard socket types.
2) Most of this can usually be worked around with a bit of creativity, such as zip ties, rotary tools, and fashioning your own extensions for mounting brackets out of spare Bic pens, etc.
3) Always remove thermal tape/paste pre-applied by the manufacturer and clean with 97%+ rubbing alcohol before applying a proper layer of something like Arctic Silver. Not only do manufacturers normally use too much, they also tend to use some generic crap that won't do squat anyhow.