I saw CC has "Monster Subwoofer Powercenter Surge Protector" on sale.
How useful is it? My unit is already plugged into a normal surge protected power strip.
- Is there noticeable sound quality difference by using the Subwoofer Surge protector (it claims it deliver cleaner power)?
- Would a normal surge protector offer enough protection again surge?

If you already have a quality surge protector, I can't see this offering much of an advantage than perhaps a smaller/neater package.

In terms of sound quality, any decent amp should have a decent power supply. It's the power supply's job to regulate the power. All power supply's have a input voltage that is acceptable and unless your power is way outta spec there isn't much of an advantage. Of course that's MHO and there's the other side of the fence :p

I think most common surge protectors limit the amount of current that can be drawn at a time, therefore limiting the energy an amplifier can put into either speakers or subwoofers. That's why it's generally better to plug those straight into the outlet than a generic surge protector. I don't know if the monster one improves upon that, but I do know that every monster product is way overpriced and has superior and cheaper counterparts from other brands.

panamax/furman addresses the high current amp surge protection especially the
furman model for 20amp.

You would have to compare the joule rating to find out if it has more protection. I have this unit and I think it is rated for 1000 joules. It does use choke filters and capacitors to clean up the AC line noise if that's important to you.

I don't think current draw is going to be much of a problem as most sub amps use efficient icepower amps. If you are plugging in a Krell amp then that's a different story. :D