Quoted from too-many-pins:Don't overlook Data East titles - some of them can still be bought fairly cheap compared to other similar machines. One of our favorites is Laser War - fun with great light show and still can be had for under $1500 if you are not in a rush. That would give you $1000 to $1500 for a second machine!
If you only have room for one and want to spend closer to your $2500 Whirlwind, BSD, and WCS 94 are all solid choices. Pin-Bot is another great choice that can be bought for $1500 to $1800 if you are looking for the cheaper end of things.
Agree, Laser War and WCS 94 are fantastic pins for what they cost!