Price Paid:  $349.00 from eBay - SurfAlan

Summary:
For the price I paid for this subwoofer you cannot go wrong. There is nothing in the sub-$400 price range that will even come close to this little beast.
You'd spend around $500-700 to get a fair competitor. I'd say the sound is a tad on the loose "boomy" side, but anytime you buy a sub with a passive radiator you should expect that type of sound. The other subs I compared in the $500-700 range sounded great, but not head and shoulders above the Earthquake. In fact, the Earthquake sounded better than any of the $500-600 offerings. It wasn't until I got into the $650-750 range that I felt I was actually outperforming the Earthquake.

In summation, for $349 you cannot go wrong with this sub.

For those who are curious, I am running a Marantz SR7500, with Paradigm AMS300's in the front, Paradigm AMS250's in the back and a Paradigm CC-370 for the center. This sub performs very well in this setup and I couldn't be more pleased with the performance vs. price ratio.

Strengths:
Goes very low for a 10" sub.
Compact size is easy to place discreetly.
Very solid build - radiator and subwoofer are built to last.
Very easy setup and controls are simple and effective.

Weaknesses:
Takes a few seconds to kick in when it get a signal from the amp, but that's just being ultra-picky.

Similar Products Used:
Polk PWS-350, Paradigm 1000, RBH, Energy, Klipsch

Price Paid:  $350.00 from ebay

Summary:
I purchased Earthquake's MKIV-10 subwoofer about 4 or 5 months ago, and when it arrived it didn't look that impressive I'd have to say, the sub itself is fairly small in size. It took probably a good 30 or 40 hours of music to break it in and really get the bass that I wanted, and I'd have to say I'm really pleased. For buying this sub for 350$ it was a steal, I bought it on ebay. You'd never know it was only a 10" sub, as is cranks out the bass straight down to 20 Hz, doesn't choke or get boomy!! I'd reccomend this (or even better their more expensive subs) to anyone, the bass is very clear, and absolutely rocks my room!! My friends can't even stand to be in the same room when it's all the way up!!

Strengths:
A real bargain, very clear and well defined bass, doesn't choke at high volumes or at low frequencies.

Weaknesses:
none that I can think of