Look at different exchanges, they all have limits on what you can buy.  Also look at the fees, they can eat in to your money.  Right now it seems like cex.io has the lowest fees, but I didn't look at every exchange.  They don't charge anything except their regular trading fees.  So you will end up paying for wire transfer fee(s) and .25% to buy btc.  There may be better but that is the best I found.  Also before buying look at the order books.  There is no point in making a price spike because you will pay more than you need to.  With that size I think that what others have said, making smaller purchases at multiple exchanges, is your best option.  If you use LBC just make sure you are not getting too much markup, the % can be (but is not always) pretty steep there if you are not creating your own order.

Best of luck!