but the 7.62x39 has more "ooomph", you know, and I personally have experiance shooting the cartridge with an SKS. Is the ammo accurate, or is the cartridge itself crappy for accurate, plinking, and cheap? Or should I concentrate my interests on .223?
There is 'accurate' 7.62x39 ammo out there, but you aren't going to buy it for cheaper than .223. Wolf and a few surplus sources for 7.62x39 is (more like was) cheap a few years ago, but accuracy isn't very good- its cheaply made ammo. The 7.62x39 is capable of excellent accuracy, but to get that, you'll pay $15 a box for the ammo or will have to handload it yourself. On the other side of the equation is the 'cheap' .223 ammo. You can buy remanufactured balck hills ammo for around $20/50rd box, and for even cheaper, buy Ultramax (though I don't necessarily reccommend Ultramax) and you'll get decent to very good accuracy.
I don't think 7.62x39 ammo is going to be any more readily available than .223- it was very difficult to come by last year and was about 2x the normal price if you could find it.
I would highly reccomend an AR in .223, if you need more oomph, you can get an upper in anything from 6.8 SPC to .458 socom. I'd save the 7.62x39 for the plinkers and noisemakers like the AKM and SKS or for a bolt action if you really are interested in reloading it.