I'd say Dredd, hands down, but you've already owned that one.
Corvette, surprisingly, can be had in that range and is one of the most underrated games now. Demo Man, Roadshow, World Cup Soccer, Dracula, Shadow if you can find one that cheap, are all good options.

Also, if you have space you could get two solid alphanumeric titles. Any two of the following: Pinbot, High Speed, Atlantis, players Whirlwind, F14, Space Station, Taxi.... if you're not terribly hung up on condition, there are tons of great options.

Also, you could get 3-4 good early solid state titles. Embryon, Mata Hari, Meteor, one of the better Gottlieb System 1 games, Harlem Globetrotters, Eightball Deluxe LE, Flash, Laserball, Future Spa.... the list of great sub-$1k titles goes on and on and on.

Personally, I'd take this chance to diversify and get a few great earlier games. If you've got space for multiple titles, that's by far your best option.

It really depends. In the sub-$1500 range for DMDs, you can't do better than Lethal Weapon 3. However, looking at games up to $2000-2500, you can get into a B/W title like Demo Man that blows away most Data East games in that range, except Jurassic Park. Once you get up into the 3s/4s, several B/W games are better than Guns N Roses.

If you throw in Segas and Sterns, you can get into a Nastycar in the low 2s, which is probably more game than most anything else at that price. Also, though I don't have much time on it, Batman Forever seems solid.

Not to say Bally/Williams games are head and shoulders above Data East/Sega/Stern, but good value for money is more readily available with B/W games; probably due in part to higher production numbers.

That's what you'd gun for at $3k?
Ready, aim, misfire.

TSPP is closer to $4k. Last one I saw in the low 3s was $3200 two years ago, and needed several playfield mechs worked on (though the boards were solid.)