yes, return the FX5600XT and get yourself a GF4TI, FX5700NU, or better
GF3TI... ya it's probably better than a FX5600XT too. The FX5600 competes with the GF3TI in most benchmarks, so I can only imagine that the weaker XT version is probably worse than your average GF3TI. But I don't think you should get a GF3TI since it's showing it's age.
And trust me, everyone will tell you that 128 RAM is not enough to game
Athlon64 3200 Clawhammer / Asus K8N-E Deluxe / 1GB Crucial DDR400 / Geforce 6600GT 128MB AGP / Windows XP Pro