Bah.
From my DMing experience, the whole CR or EL thing is more art than science. You can debate mathematical theories for this and that, statistics for the other or whatever... but it comes down to what your party can and can't do.
Example:
My party consists of four 20th level PCs. There's a wizard, a paladin, a cleric and a ranger/rogue. Pretty average. The foe they encoutered was a Pit Fiend - CR 20. Now, they did beat this encounter. After the forth try - and two near deaths (-9 HP!) for the paladin. Mechanically, they should have defeated this monster with moderate effort. Their lack of decent tactics, and effective use of their resources nearly killed the paladin twice. (Note: if you are the main line fighter, it's not a good idea to charge the Pit Fiend while your support is 30-40 feet away.)
Same party, a few days later:
They have managed to get to the final BBEG of this section of the campaign. The BBEG was a 20th level sorcerer death slaad, with several 17th level death slaad buddies, and some 18th level grey slaad fighters. They mowed through the buddies in about 3 rounds, with only a small percentage of HP loss. Then they reached the BBEG - who they had been chasing for months (and to whom the Pit Fiend mentioned above was a lackey). Well, needless to say they nearly had him dead in two rounds, while he had yet to even scratch a PC. So, in good DM fashion - I faked it. I made some slight "on the fly" modifications to the BBEG, and gave the PCs some trouble.
(I knew that they would waste him in the end, but since this was supposed to be a climactic battle with the mastermind they had been persuing. As a player, it would pretty much suck if we killed the BBEG in seconds - that battle needs to be fun and last a while. Now, I didn't tell my players that I modified the BBEG, but they did really enjoy the battle. They commented several times how difficult it was to beat him. I could also tell that the difficulty of the battle made it mean something. They appreciated that.)
Anyway, you use should CR and EL as guidelines only. They become nearly meaningless without a party to put them in context. If your party all have armor of Heavy Fortification, a rogue 10 levels higher than the party isn't much of a challenge - they're immune to it's power. If they all have rings of Fire Immunity, then a Fire Elemental isn't really a challange, no matter what the levels or CR. Conversely, a party of 3rd level PCs without appropriate armor will face a challange against a couple of orcs.
In order to set up a balanced encounter, you must know what your PCs can do, what they defeat easily, what gives them some trouble, and what they just can't handle. Once you know all that, then you can find a range of monsters appropriate for them - and then you can take that range and use the CRs to see if it's too far one way or the other. CR is certainly much less useful than the information about the party.