I personally like Cadence, but hey I'm a bit biased, I have 4 of there ZRS range in my car.
Soundstream make some quality products as well. The Cadence amp is more powerful but the Soundstream amp is brand new. Up to you. But there are other places to buy from, try your local store and see how much you can talk them down. A stores warranty is much better than a Ebay promise.