I went into a local music store and sat down with a blue burst Yamaha APX500. I don't remember if it was flame maple or not - I'm assuming so.
I really like this guitar, so I came home and looked into Yamaha acoustic guitars with the APX name, and there's a 700 and a 900.
Now, I'm sure that there are some bonuses with these, but the guitar wouldn't be plugged in very often as I have a Gibson Firebird V for my electric guitar needs.
Basically, I want to know if the APX900 is worth the extra $600 over the APX500.
they're nice looking guitars, but if you plan to play it unplugged, i suggest you go back and play them a few more times. they have a very thin sound unplugged - i really wanted one because i liked the thin profile and the look, but after the first buzz of seeing and holding them wore off, i realized that acoustically they didn't deliver at all.
Before playing the APX I played an FG160, and I find that this guitar sounds much better than that one. Of course, I mostly play bluesy stuff (Robert Johnson, for example) and I need a guitar that's easy to play like this one. The only reason I'm ditching the old FG is because the neck is warped beyond repair. Which is to be expected - I got it for free from a Salvation Army dumpster.

While playing in open D minor tuning, it sounded great. I was also a fan of a black Martin model that was in stock, but it had some major problems and was probably not worth the money they asked for.

But, seeing as you say they aren't that great acoustically, I think I'll pick up the 500... I have the money to spare, and if it doesn't work out for me, the guys I buy from are good with returns...
if you're interested in robert johnson style blues, perhaps you could get a parlor like mine. i have a seagull coastline cedar grand, but there are other parlors in your price range. a lot of the classic delta blues guys used parlors - most people did back then. if you want to make them easier to play, all you have to do is lower the action a bit, but part of the sound of the old blues players is that the action was high and the guitars weren't easy to play.

if you like the martin sound, you might find it from a blueridge model -

the 500 is the only one of the 3 with a laminate top, but honestly this is one of the few times i couldn't tell the difference. when you played them, could you find any difference in sound unplugged?
i own a 12 string apx 500, and it is pretty meh unplugged, but plugged into a nice DI box then into a PA, it sounds damn nice. i will be upgrading it shortly, but it is a pretty good beater guitar.

if your into delta bluesy stuff, i agree with patticake, a great option would be a parlor. being a lot smaller, there is a larger tendancy for solid woods too, i find, which makes for a really nice sound.
I just sold an APX as I hardly every played it plugged in and it really didn't sound that good unplugged. If you are going to be playing unplugged I would highly recommend getting a "proper" acoustic. I replaced it with a similar value dreadnought and the difference is amazing
I recently bought an electro acoustic and wanted one that sounded fine plugged or unplugged. Tried an APX 700 and found it was good appart from the unplugged sound which was a bit weak. In the end I bought a Faith Venus acoustic as it was solid wood and sounded good plugged or unplugged. You are doing the right thing playing a few guitars to see what you think.