I'm thinking along Koin's route myself. The mining game is starting to be BIG business, and will get to be much lower margins than right now. It looks really attractive right now, but I'm cautious about investing in mid-sized gear. Small gear should be nice, and lots of little guys are very beneficial for bitcoin. I'd be hesitant about spending $30K right now on a rig box.
I wouldn't hesitate to buy 20 mini rigs if I had the cash.
With a full diversified plan, you might be able to make a go of it, but there's a fair amount of risk involved. At the moment, I would be uncomfortable with more than 30% of my portfolio in on-site mining operations (and gear)
I see a thread on a potential large ASIC mine going in (min 1THash). The threat of arms race escalation in mining is significant. The effects on difficulty, and change in block reward are risky variables.
FPGAs are changing the game, but ASICs will do it completely - this will separate the men from the boys (and the women from the girls!) - The days of mining bitcoin in your house as a money making hobby are gone. $30K is a lot to find out you've spent on a really expensive, kinda boring, hobby. I'd buy a horse instead
There are businesses to invest in, funds, leveraged trading...hell yeah, even naked Credit Default Swaps if you're into that sorta thing. And mining. Lots of mining issues available (stocks and bonds).
50GHash sounds super sweet, but there is a lot of hardware on order that won't be shipping for several weeks that will start to hit the network all at once, and likely punch the difficulty
Good luck!
EDIT: One point I disagree w/ Koin on:
I'm all in - This is something I believe in, and I have no trouble risking everything on it.
But I am diversified within bitcoin
