Darren,
You may be thinking of the AXON award which is available only for Hilton AMEX holders. It is a 4 day award in a Cat 5-6 hotel for 125K (normally 140-160K). Not quite 5 for 4 but a diso.... for 4 nights.

There is also a GLON award only for Gold/Diamond HHonors members.
6 nights for 150K in Cat 4-5 hotels (normally 180-210K)
6 nights for 175K for Cat 6 hotels (normally 240K)

Hope this helps