Consider this: you lose money if you hold cex.io for any significant period of time, but cex.io mines more than an Antminer for the same price. Thus, you lose money even more if you mine with an Antminer. At the current prices, you should do neither.
To make a reasonable profit by mining, you can't pay more than 0.015 BTC per GH/s.
My plan is to re-invest the payouts into additional GH/s so that my overall payouts increase by their rate of occurrence and volume. just not sure if I can do it fast enough to keep up with the difficulty changes...
You can't keep up with the difficulty because the price is too high and the mining revenue is not enough to buy the lost mining capacity.
Thanks for the advice, I'll take all of this into consideration before I make a decision.