Red Octane is high quality, but pricey. buynshop (
www.buynshop.com) is much better bang-for-buck, and they have an entire line of pads to choose from. You can't buy a decent quality pad in a store, as far as I know. There are PS->XBox adapters, but I have no idea how well they work.
I've played on the following pads:
BNS (buynshop) Ultra-NX (briefly)
Homemade hard pad
Red Octance Ignition (older, I think 1.0)
BNS Ultra-DX
My "best value" recommendation is the
BNS Ultra-DX, but a pair will set you back just over $100 with shipping, which is a little rich, especially if you don't know if you like the game. Maybe you should get the store pad to get a taste, and jump to the Ultra-DX if you like it.
store pad ($20 + tax)
+ some durability -> BNS Ultra-NX ($35 shipped)
+ hard foam -> BNS Ultra-DX ($65 shipped)
+ surface texture -> Red Octane Ignition (~$100?)
The hard foam keeps the pad in shape (zero bunching, helps a little with sliding) and cushions your feet. When we played on tile (over concrete), we put down carpet padding that we had lying around. The only functional difference in the Red Octane pad is that the surface feels better than the BNS, which is sticky with bare feet. Socks feel the same.
Here's a guide I found on soft pads:
http://www.cs.rochester.edu/~balazer/ddr_soft_pad_faq/