I love my acoustic and I play it as much as my others put together. It's a Dean EABC strung with D'Addario chrome flats. If I had to pick my one sound, this would be it.
Like you say, it's great for picking up and playing any time. Kids in the tub: bring it to the bathroom. Kids watching a movie: it doesn't distract them. And I'm not trapped in a set of cans when I want to practice quietly. Family sleeping: doesn't wake them up. Play it on my balcony w/o bugging the neighbors. Learning a new song or mastering a new piece: my ears aren't assaulted with amplified mistakes. Bring it on vacation or even just weekend trips w/o dragging an amp along.
Here's one on eBay:
http://www.ebay.com/itm/Dean-EABC-Lefty ... 2219897825Mine needed a bit of touch up when it arrived, although not much. Had to take the saddle out to clean some gunk off the transducer that was making my string volume uneven when plugged in. That was a ten-minute fix. Had a luthier file down some sharp frets after the first New England winter with it. A tweak of the truss rod when I switched from the stock phosphor bronze to flats. That's about it, though.
I didn't get it for jamming. I've only played with others (guitars, uke) for one weekend and it definitely wasn't loud enough to keep up even with acoustic guitars. Amplified it could be nice, although you'd want some kind of preamp for an EABC like mine because the pickup is all passive--I've had luck with a SansAmp ParaDriver, but I barely use it. If you step up to the Dean Exotica, the electronics are supposed to be very nice. Pete here owns one and has it strung as a tenor bass, I believe.
There are a few different models to choose from in your price range. Here's what's at Adirondack Guitar, which is where I got mine:
https://www.adkguitar.com/collections/a ... eft-handedIf I ever get a mind to upgrade I would love to try a Boulder Creek, but I haven't seen a 4-string for sale in a long time. But those are more like $800 anyway.
Oh, and almost forgot, a few different companies, Dean included, make resonator models. Not sure I'm crazy about their sound, but I would love to try one in person one day. Here's a fun clip of one in action:
https://www.youtube.com/watch?v=L0fyYBXVaCUI've also been eyeing a GoldTone MicroBass lately. Even more travel worthy, and sounds great plugged in. I think Matt R. here has one. RondoMusic has a knock-off version for $150, although it's out of stock now.