Gut says BOS, but Green-tinted glasses aside it'd be a tough series.
I think we'd win - especially if we went with our "small" lineup of
C - KG
PF- Posey
SF- Pierce
SG - Ray or TA
PG-Rondo (or Eddie House for offensive punch)
Sprinkle some Perk in there to ruffle Pachulia's feathers (Neither he nor KG got along with Pach AT all, it seemed). Between those two we'd get a technical free-throw out of Zaza (or the Refs would tee "US" up, lol)
The lineup I just mentioned would cover them defensively...to a considerable degree....BUT we'd struggle to score some so I'd be hesitant to use this lineup often without Ray Allen in there.
Ray wasn't a great defender but in 08 I'd give him a decent rating - and with his potent offense I'd struggle to keep him off the floor.
To be fair I don't think that Tony Allen "fully blossomed" defensively until he got to MEM, though...even though he was still a decent defender in 08.
Tip the intangibles towards us - with KG barking out defensive assignments and Pierce being Mr. Do-Everything I'd love to see such a series.