4-tabling $25NL? Definitely get GT+, and probably PokerAce HUD if you feel you've got a free $25 (I've never used it myself, but everyone raves about it).

Just knowing VP$IP of the players acting after you to help in decisions about preflop actions is worth it for me.

It did take a little while to get used to using it though, and that little while was a downswing due to inexperienced HUD usage.