Here's the deal on potting mixes. It ain't rocket science. It really boils down to the fact that you need 3 different components in a good container mix, which you can either get by buying a pre made mix, or by making your own using the three components. Here they are.
1. A container mix must provide a light, fluffy structure which gives the roots some space to grow and explore, as opposed to being tightly packed and heavy and dense (like clay or garden dirt, etc). You want this "structure" material to not absorb too much water, or then you'll constantly be getting water-logged, heavy, and will be susceptible to virus/mold/bugs etc. One popular medium that provides a nice light, airy structure that peppers like is: peat. Peat is a really good medium for pepper growing. ProMix is 80-85 % peat by the way.
2. Since peat has absolutely no nutitional value, many people will add compost to the peat, to create a still-fluffy but now-somewhat-heavier mix which has nutrients for the plants. A peat-compost blend is not going to be as light and airy as just peat; it will get watelogged and will be heavier, but it will provide good nutrient value to the plant. I personally mix 75 % peat, 25 % compost, to get some nutrient value but still mostly leaning toward light, airy mix.
3. You need effective drainage - to suck the water out of the container, and you also need to retain some moisture so it can be used by the plants. A few handfuls of vermiculite and perlite play exactly these roles.
So basically, if you used 2/3 peat, 1/3 compost, and thew in some vermiculite or perlite, you'd have a very effective mix. This mix in fact would be roughly consistent with what the Square Foot Gardener (SFG) book says to do, and also this mix is roughly what is in ProMix BX, but at a considerably lower DIY cost. It is also easy to tune this mix for other plants. For instance, if you are growing plants with higher nutritional demands than peppers, you can just make it 50/50 peat/compost.
Personally I would avoid those MG potting mixes and the like. Every time I open one up I am deeply disappointed in the quality. I think you are better off with a big fat bale of peat, a couple bags of compost from the local garden center, and $5 or $10 bags of perlite or something. That mix will be much, much higher quality than anything you're going to get out ot a MG bag.
One thing, get a small bag of dolomitic lime and add it conservatively to the overall container mix. Peat on its own is or may be too acidic for some peppers, left untreated. Applyling the lime will take down the pH to a range more comfortable for peppers. Some people get pH meters and all that jazz, but in truth, you can just assume a peat mix will be a little acidic and add 1/2 or 1/4 of the amt of lime it says to add on the lime package, and it'd be fine.
I'm going to repot that one also. Basically what I'm asking is if someone can give me a general soil setup that should work to get me started this year and next year once I learn more I can try different setups. 
