You may find a bit of biased towards the Olds on this site, however you cant beat Acura and its track record of having decent cars.
Best bang for the buck...I'd say Aurora, its conservatively styled over its previous generation model (see below) however the interior is pretty impeccable. Don't be deceieved by the 4.0L V8 in the 2nd gen, the car is pretty light (for its size), very revvy and delivers decent punch. It wont have the off the line grunt of the Bonneville, but its evenly distributed power across the board.
If you want even more biased opinions on the Aurora
I prefer the new 3.5RL over a lot of cars on the road right now...so its a toss up.
Good luck with your choice.
( I hope you go Aurora hehe) what colour is the car?