River value bet or check behind?

[redrooski24]

Wasn't too sure what to do on this river since the card froze me up and I definitely thought the A could have improved his hand.

PokerStars 5/10 Hold'em (10 handed) converter

Preflop: Hero is MP1 with K[img]/images/graemlins/club.gif[/img], Q[img]/images/graemlins/spade.gif[/img].
<font color="#666666">3 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#666666">4 folds</font>, SB calls, <font color="#666666">1 fold</font>.

Flop: (5 SB) J[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, <font color="#CC3333">SB raises</font>, <font color="#CC3333">Hero 3-bets</font>, SB calls.

Turn: (5.50 BB) 8[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, SB calls.

River: (7.50 BB) A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, Hero ???