Originally Posted by
Blades
They're good.
However, I would never admit this association in any sort of real life venue.
In all seriousness, if you enjoyed those tracks you should look into any of the other works of Jun Senoue, who is responsible for most of the duo's music. He is a talented and unique composer who really shines to my ears. The hard part was finding the music, but I would imagine it's quite a bit easier nowadays with the widespread reach of the internet. When I first got into his music, the internet wasn't nearly as helpful (2002-03) so I essentially had to buy most of the albums (and got zapped by bootlegs! Those are the worst).
However, you should really play the games and experience the music through them first as that provides more of an impact if you're into the whole experience, in my opinion.
If you're looking for stand-out examples, I always enjoyed the work of the Sonic Adventures and Shadow The Hedgehog. Another great soundtrack is the one from Sonic The Hedgehog '06. One can tell that a large amount of work was put into the music. The soundtrack is otherwise let down by the less than stellar game itself (unfinished rather). There are others but those are good starting points.
Otherwise just start looking through and see what you like, discovering new music is one of my favorite activities.