Compression is key for getting the kick to have a nice even sound. But it will not add frequencies which are not already present. It just helps make the kick a more consistent tone. It also can add some snap to the attack if used right.
Starting with the proper kick in the first place is key. NEVER layer sounds which sit in the same frequency range. As you stated, it only serves to cancel each other or create phasing issues. The only time you should be layering kicks is if you love the low end of your kick but feel it needs more snap, or the other way around... You like the snap a kick has but want more low end. If and when you do layer the kicks, make sure you eq them properly at the crossover point you decide so none of the frequencies overlap. I usually cut over at 150 or 200 depending on the kick. Sometimes I go as low as 90 or 100 though. All of your sub will come from around 60 and below. The real power of a kick though is between 80-100. Alot of house music has kicks that peak all the way into the 150 range. Alot of people will use a kick that peaks between 80-150, then layer a higher kick which they use an eq to accentuate around 6 Khz for snap and bringing the kick forward in the mix, depending on the kick obviously. You will want to compress your low kick different from your hi kick, then you will want to apply even different compression to the both so they sound like one sound and not two seperate sounds. You also want to make sure that you scoop out some of the material in the middle if it is present, to make room for your other sounds as well as removing any "boxiness" to the sound. The boxiness usually sits between 300-500 hz.
Of course I am talking about subtle compression and eq here, nothing extreme. You would be surprised how little is actually needed to make a difference. Another thing about getting your kick, bass, and drums in general to sound phat and pounding is proper gain structure. You want to process your individual sounds first and have them sound nice and even. You then want to setup a bus channel for all like sounds and process that. The processing on the individual sounds should be to get them to sound even, not to make them as loud as possible. The bus mixes is where you want to introduce volume.
As for basses, layering is key. Similar to the kick, the sub will come from 60 hz and below. Warmth comes from 100-250hz range though... so you will want a sound which has your sub content and a sound which has your warmth. A sine wave works good for this, but sometimes a triangle with some filtering is even better as it has higher order harmonics in it which add warmth. It's common to use a triangle and hi-cut it from like 150-100 depending on the mid bass content. You will also want a mid bass sound which gives more warmth and depth to the bass sound. And I always put a higher layer because the music I write centers around the bass and it plays the lead most times... so I want to maintain interest and I do this with the higher layer from like 1 Khz on. I will process the shit out of it with distortion and guitar amp plugins, and then chop it up and make a rhythmically interesting texture that sits on top of the other two layers. I am then free to automate stuff on the high bass without taking away from the mid and sub... things like filtering, delay, and modulation fx come to mind... EQing everything obviously so no frequencies collide. Then using proper gain structure so that all parts gel and create one powerful bass...
Sidechaining will help seperate the kick and the bass so everything is not one big horrible messy blob. It basically ducks the bass out when the kick hits, and then the bass comes swelling back in. There are other ways to keep the two from conflicting like EQing or timing, in other words make sure the kick and bass never play at the same time. Like classic house style where the kick is on the downbeat and the bass notes are on the up beat...
Hope this helps in your quest for phat bass and pounding kicks. Not sure how much of this applies to your style, as this is geared towards bass driven music.
