50NL: Does this turn bet mean I'm committed?

[RunDownHouse]

Villain is a multitabling TAG, but we haven't tangled, so no reads other than that.

When I bet this amount on the turn, do I have to call a shove? If I want to try a bluff, can I get away with less? If I have Ax, should I bet at all? I mean, he's going to have a tough time calling with something like AT, so it could be combo bluff/value, right? I guess I'm wondering what hands, if any, such a line is correct with.

PokerStars No-Limit Hold'em, $0.50 BB (6 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Hero ($49.70)
BB ($47.50)
UTG ($53.60)
MP ($137.65)
CO ($59.20)
Button ($59.65)

Preflop: Hero is SB XX.
<font color="#CC3333">UTG raises to $2</font>, <font color="#666666">3 folds</font>, <font color="#CC3333">Hero raises to $6</font>, <font color="#666666">1 fold</font>, UTG calls $4.

Flop: ($12.50) 6[img]/images/graemlins/diamond.gif[/img], 2[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $9</font>, UTG calls $9.

Turn: ($30.50) 2[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $20</font>...