the Behringer GDI21 is basically a clone of the Sansamp GT2, I don't have any experience with it myself but i do own 2 of the acoustic versions and am very pleased with them, the bass version is also very popular as a backup DI in case of amp failure.
for the cost you really can't go far wrong, the cases are plastic and the switch and controls feel a tiny bit flimsy but for the price they are generally excellent.