I've downloaded OP8's Slush. It is a pretty solid album. Cracklin' Water, Lost in Space, the title track, It's a Rainbow(Devil Loves L. A is the only weak track) are some of the nicer tracks on it.
As for Giant Sand I didn't particularly like Love Songs but Chore of Enchantment is pretty good. Overall though I'd say they rarely reach the heights calexico reach.
I've also heard Calexico & Amor Bellhom Duo(
http://www.amormusic.com/goodies.html ) album called Tete a Tete which has the very impressive Gilbert (probably one of the best Calexico songs) and The Wrestler's Masque (which is a 14 min song which picks up only at about the 9 min mark and turns into quite an impressive experiment).
