Ok i have narrowed down my decision to these two subs.
Now my room is fairly small, *11 x 11 x 8*.
Should I go for the A3-300 in this small room, will it be overkill?
The room is a square and the sub will go in the back rt corner (no other place to put it as of now).

I think you'll be fine with an A2-300. That's a pretty small room.

No such thing as overkill as it just gives you more headroom to work with.
But in that small of a room the A2-300 will give you a good amount of bass.
What subs have you owned in the past for frame of reference?

go for the bigger sub

This is my first ever home theatre sub.
I ended up ordering the a3-300, go big or go home!
I will be moving soon, so having the better sub will benefit me since my new place will be bigger.

I haven't heard the A2-300, but I have the A3-300 w/upgraded driver in a room that is about 15x15x18 with openings to a galley kitchen, small hallway, and entry way. The sub is way more than I "need" and I rarely turn it up too much. I typically keep the gain around 11-1:00. I love it, just don't underestimate the footprint it's larger than my end tables.

Dual a2-300's would have rocked.. Then again I am a big dual subwoofer fan.

As everyone mentioned.

The A2-300 will be plenty for that room, but if you are willing to spend the money, an A3-300 with upgrade subwoofer will give you a little more output, more extension, and a little better sounding setup.

Either one will work great, with the A2-300 getting my vote.