How to judge comfort when buying a new saddle I bought a Motobecane Mirage S recently from bikesdirect.com

I took the following advice from a bikes forum:


  Plan on changing the seat, pedals, and possibly the tires. The seat
  will make your butt feel and look like a loose meat sandwich, which
  will be the outcome on just about any road-bike you buy for under 
   $1000.00.


Because I am on a budget I bought a Selle Italia Flite seat on craigslist for only 30.00 

I see reviews saying how comfortable this seat is even on long rides but when I feel it in my hands it feels significantly harder than the seat that came with my Motobecane Mirage S.  I was hoping someone could shed some light on this counter-intuitive phenomena regarding saddle hardness and whether it will actually perform better on long rides and more importantly, why that would be?
This article, The Four and a Half Rules of Road Saddles, from Cervélo Cycles has been really helpful to me when pondering saddles. I think the key points are:


The saddle needs to be wide enough to support your "sit bones" but not so wide that it chafes on your thighs.
The saddle has to be flat enough that the part between your sit bones doesn't press up on your soft tissues.
If the saddle is padded, make sure the padding doesn't defeat the flatness.
A cutout might help.


Also make sure that you've got the saddle adjusted well. Make sure the height is high enough, but not too high (I start too high and work down, because it seems easier to recognize too high than too low). Also make sure that the saddle is level – nose up can make the pressure worse, nose down and you may feel like you're slipping off the front to the saddle.