Maiden is excellent once you get a feel for it, I didn't like it much at first either. However, ultimately it's similar enough to Godzilla that it's probably not what you're after. You were on the right track off the bat. Centaur and TNA are great; a good classic, straightforward pin is a great palate cleanser from a long player like GZ, and both of those are awesome. Others to consider:

Seawitch, Meteor, Stars, Ali
Black Knight, firepower
Black Hole, Haunted House

Alice Cooper is great too, if you want something more modern but very different from GZ.

Original or 2K Black Knight. I do like BKSOR, but those are a better contrast to GZ.

Honestly, it's not to hard to move pins nowadays, and with older stuff you're looking at the 2-3k range or less, other than a few desirable ones like centaur/fathom, or rare stuff like Star Gazer. Sounds like you were budgeting around twice that - I'd just pickup the first TWO games under 3k that sound kinda interesting, play till bored and trade or sell for something else until something sticks. Worst case right now in that price range you lose a few hundred bucks to get something to move quicker, and I figure a couple hundred to "rent" something at home and see if I like it is a good deal.

Glancing at the marketplace this morning, I see an FP and FP2 up in your area. My in-laws have firepower 2 and I quite enjoy it, though I think I prefer the original on the whole.

If space is at a premium, some other things to consider:

1. This won't be a permanent add, and shouldn't be. With that in mind, I'd worry less about exactly what I got and just make sure I picked something up that wasn't too hard to get rid of at a reasonable price. TNA, for example, is a great game but may be difficult to move unless you're willing to take a fair loss. I'd love to have one, but I could pick up a centaur and a firepower for that - think a lot of folks feel that way unfortunately.

2. On that note, you might do well to think more in terms of what you'd be okay with spending to "rent" a game for 2-4 months. As in, if you're OK with losing $500, $1000, whatever in order to sell/trade for whatever you want next. That makes it a lot easier to figure out what you'd be okay with bringing home to try out for a while. You can probably pickup a TNA for 7-8 right now; at 6-7 you could sell one pretty fast.

3. Everyone beats up on virtual pins, but maybe consider picking up a really nice one for a while? It's "not pinball," but it is a GREAT way to try out tables and see what you might really want to bring home from the older stuff. The custom build ones can be pretty cool, but even the smaller at games Legends gives you a way to checkout rulesets and play feel for things, and they are practically giving those away right now.

My 2 cents - talk that guy selling the centaur in Jersey down a few hundred bucks (playfield looks beat up). It's a GREAT game, you know you like it, and it's popular enough it won't be too hard to move if you get board. Or, if you love it, you can learn to do a playfield swap and order one from CPR

Yeah, that's what I'm saying - don't plan on making money or breaking even, just figure out what you're willing to lose moving on to the next pin if space is tight. Trust me, very few games are gonna be so amazing you want to keep them forever if you can only have two. Just too many good games out there. I kinda think in terms of "renting" - what am I cool with spending to have this game around 3-6m (i.e., losing when I sell it)? If I only ever brought home the one I wanted most, I'd either never get a new one or bring home 5 at a time

That said, if you're smart and patient on a decent deal, most pins retain their value pretty well nowadays.

And I don't know if Centaur or TNA is "more desirable;" both are well appreciated but I think at 4-6k it's easier to move a centaur if you get bored with it than a TNA at 7-9k. Also, I love me some centaur

Also, FYI: if you look up any game on pinside and scroll down, you can see all the archived ads for it - if they sold, how fast, and how much (some folks don't disclose that though). Pretty easy to figure out how easy it'll be to sell or trade something if you decide you don't like it. If you get sick of GZ it could be gone tomorrow for the same or more than you have in it; buy a Mando NIB and you better learn to love it or plan to spend a month trying to sell it for a lot less than you paid

It's not a DMD; it's a different style of cab entirely. Leftovers from a game called rapid fire, they did a run of centaur and eight ball deluxe in it. As far as I know, the games are identical except for the head style. They're a bit more of a bother to move, but they go for about half the cost of a regular centaur and play the same I believe.