Fuck buying online.
Go to your local record store, your used music store, your big superstore, WHATEVER. Some of the cashiers know more than they get credit for, and can point you in the direction of some stuff that may gel with your tastes.
To get the most bang for your buck, HMV occasionally does stuff like "2 for $25!" deals. That's how I got the Death From Above cd, and I picked up like 6 Floyd CDs off there. Not just DSOTM either. Animals, Meddle, Piper At The Gates of Dawn.
Get out there and do it in person.