I am thinking about purchasing a 3TH mining rig and would like to know if it is still worthwile me joining a mining pool to mine BitCoins?
Do I have enough power to go it alone?
You probably want to still join a pool. Even if you lose 1% or so to a pool, consider the cost of wasted time when down. Suppose you get ready to close down your mining rig and it has been mining for two weeks straight with no block. Hypothetically you could have received a block the following day. That means you just wasted those two weeks of computing for nothing. Had you joined a pool, you would have at least gotten paid for those two weeks. Pools will also be there for you when that two week block period turns into a two month period.
It is hard to decide right now, knowing that till you will buy, and the company will deliver your hardware, the difficulty will change many times.
Right now with a current difficulty, solo mining with 3Th/s will give an estimation of mining a block in 2 weeks (during this two weeks the difficulty may change). So even right now I would rather have a steady 2 BTC per day then to risk. Especially if after buying this hardware, you need to break even as fast as possible.