My wife and I are going to London and Amsterdam from 12/24 - 12/31. We're using Hilton points in London and the last night in Amsterdam (at the airport due to very early flight), so I'm OK splurging for the Amstel on the 28th and 29th while using my Six Continents one night free coupon. Reservations quoted me a E455 rate for a superior room, which I took. I see that I can get an E420 rate for a standard room on their website. So two questions:

1) By spending a few extra dollars to book a superior room, am I more likely to get upgraded (per Six Continents perk) to a suite, as opposed to booking a standard room where I might just get upgraded to a superior room?

2) Any ideas whether a cheaper rate might be available on a room? And is the certificate good regardless of what rate I find?

Thanks!

Bill