Hey... if the sound is a 'wobbling' sound like a woowoowoo, that changes with wheel speed, and likely the loudness changes when cornering, then it's a wheel bearing.
However, the problem could be any number of things... driveshaft, guibo, differential, etc. Best to get it checked out by a mechanic before investing your money.
I'd recommend www.rmpmotors.com
... both quality, well known BMW mechanics with great prices.