Deducting a new Computer

I'm confused on the best way to deduct a computer. 
I'd put it under misc. expenses, but 1. found my expenses were over $5K and as a sole proprietor, I'm not sure if there's a limit of under $5K, and 2. saw a note that those items should not include depreciable items.

While I would hope that I will be in business over the next 5 years, I'd just wanted to expense it but keep seeing the 179 depreciation, there is also a 100% Special Depreciation Allowance and I've seen something about Safe Harbor options. I'm really confused.

I've come to understand that I'll NEED to use said computer for the next 5 years solely for business if I choose the 179 option (taking it as an expense now), but I'm unclear as to what:

 - the 100% Special Depreciation Allowance would mean for me 
OR where to find the a Safe Harbor and whether it's a good option for me.

Is there an way to expense the whole thing now without holding me to 5 years (I'm even concerned as to what would happen if it doesn't last 5 years).
Thanks!!!