How agressive to get with 2 pair?

[rubixxcube]

I am somewhat new to 6 max and in general the game is much more aggressive, which i like. The following hand came up and was just wondering how heavy on the gas do people get in something like the following hand:

PokerStars 1/2 Hold'em (6 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is Button with 9[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">1 fold</font>, MP calls, <font color="#666666">1 fold</font>, Hero calls, SB completes, BB checks.

Flop: (4 SB) 9[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">SB bets</font>, BB folds, <font color="#CC3333">MP raises</font>, <font color="#CC3333">Hero 3-bets</font>, SB folds, <font color="#CC3333">MP caps</font>, Hero calls.

Turn: (6.50 BB) 2[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP bets</font>, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">MP 3-bets</font>, Hero ????


Do you just call at this point assuming he has a set or do you cap?

Sorry if this is standard/Basic.
Thanks,
Ruby