In my experience, most of them carry lines that have minimum advertised pricing - you're not going to see price stickers below MAP for many things due to this. My suggestion is when you're looking for something specific (like your major gear), do your research to find what you're looking for -either a specific brand/model, or specificiations (e.g. a 7mm full suit, or a mid-range regulator set) and shop around - do your research to know what you can do pricing wise online, then see who will offer you the best deal on the sale *and service* - both pre and post sale.
If the retailer lets you try stuff on, or even better try things out in the pool, that should count for something. Ask if they can do better on pricing if you know you can save a bunch going elsewhere - many times they can move a little - possibly not matching "the internet", but factor in convenience (for you) and the service they've provided. If you're buying multiple pieces, most can put together a package deal that will bring the overall cost down (in my case, when we bought Regs and BC's, as a package with some cylinders, we basically paid MSRP for the Regs/BCDs, but the cylinders were basically free)
I'm not sure what's down that way, but if you're willing to drive north a bit there's a few up this way:
Brass Anchor (Frederick)
Undersea Outfitters (Finksburg)
AquaVentures (Cockeysville)
Underwater Playground (Edgewood)
Diver's Den (Parkville)
(I'm sure there's others I've missed - I didn't intend to exclude anyone on purpose!)
In reality, you'll find that your car just keeps ending up at dive shops and you find yourself wandering around any that you past "just looking"