For something in the middle of the price range, look no further than this P.A.R.O.S.H. Tank. This item won't break the bank, but absolutely essential in your wardrobe. Why not also take a look at this 3.1 Phillip Lim Tank. It's an attractive option both price and quality-wise.
If you're not the one to skimp on clothes, then what you're looking for is this Marni Tank. It's more expensive but worth your money. While you're at it, also have a look at this Courreges Tank. Yes, this item is expensive, but it does not mean it's not worth it.