I used Audiocatalyst with the LAME add-on

I didn't know there WAS an add-on for Audiocatalyst that used LAME. Perhaps you meant AudioGrabber instead of Audiocatalyst?

And I have absolutely no question that when played back to back, the CD player sounds a lot brighter and crisper.

First things first. Remember that when you play a CD player, it's using a completely different set of audio output circuitry than the thing you're playing the MP3s with.

Even if you play a CD on your PC in Winamp, then play an MP3 in the same copy of WinAmp, they're going through two different signal pathways, and the CD audio is coming from the analog CD audio input connector on your sound card.

So you can't A/B a CD with an MP3 like that and expect to compare apples to apples.

The only way to compare the two is to create your encoded MP3, then use a disk-writer plug in (like the one in WinAmp) to convert the MP3 back into a WAV. Then burn that WAV as an audio CD track. Then play both the original CD and the burned WAV on an audio CD player. That's the only way to compare an encoder to an original CD track.

Now, having said that, there's one reason your MP3 might be less crisp than your CD. High-frequency rolloff. This was mentioned elsewhere in this thread, and it's in the FAQ. Most encoders will roll off extremely high frequencies unless you go into the encoder's options and deliberately change the setting. Make sure you've done this.