I've used all the built-in plugins for logic 7 and 8 Pro. I never use these stereo simulation plugins at all in my mixes because quite frankly they are junk. I believe there are decent ones out there that cost a pretty penny, but it's just not worth it.
Here's a few suggestions.
1) Copy a track, say for example a guitar, and hard pan the two left and right. Now on your copy, run a delay that is 100% wet. Adjust the time until it sounds good to you. If the part is busy though, this quickly makes the part sound unclear and muddy. If it is a more simple part though, this approach can yield good results with a very short delay time.
2) Take your original track, and send it to an aux with a reverb plugin. Set the reverb's pre-delay accordingly. Sound travels at approx 1000 feet per second (yes, I know that's not exact and there are other variables to consider, but it makes the following calculation much easier on the brain). That means that for every 1ms you set the pre-delay, the effect will simulate the source being 1 foot away and reverb'd... so if you set the predelay to 30ms, The verb will make the sound much bigger and spacier.
3) Use both a mic and your DI. I don't care if you have to go to radioshack and buy a 10 dollar mic. You will probably be happier using that and your DI, than your current situation.
As previously stated, space and depth only come from one place. You gots to use the real deal!