AKs again -- hit 2 pair on flop, reality check

[jtr]

Hello again.

The villain in this hand (MP2) didn't raise much (only about 1%) but he called with all sorts of garbage (60% VPIP) and cold-called raises 8% of the time, so he's a man who likes seeing flops. Postflop, his average aggression is 3.49. so he likes throwing some chips around, and he's won 47% of showdowns suggesting that he's happy to bet with a lot less than the nuts.

Party Poker $50 No-Limit Hold'em, $1 BB (10 handed) converter

UTG+2 ($50)
Hero ($50.85)
MP2 ($121.05)
MP3 ($49.1)
CO ($47)
Button ($52.9)
SB ($87.6)
BB ($89.75)
UTG ($48.95)
UTG+1 ($29)

Preflop: Hero is MP1 with K[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of $0.5.
UTG calls $1, UTG+1 calls $1, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $6</font>, MP2 calls $6, <font color="#666666">3 folds</font>, SB (poster) calls $5.50, <font color="#666666">1 fold</font>, UTG folds, UTG+1 folds.

Flop: ($21) K[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">Hero bets $20</font>, <font color="#CC3333">MP2 raises to $50</font>, SB folds, Hero?

I only have about $25 left. It would be utter madness to fold here, right? But then again, what do we think he has? Flopped set (presumably 5s) is certainly a possibility. A5 or K5 would be nice. AK and a tie seems quite possible also. Does he have the cojones to do this with a hand like AQ? The old all-in with the flush draw move seems quite likely too. I have to call, surely...